A planar antenna consisting of four bent arms on a thin dielectric substrate is investigated. The arms are located symmetrically with respect to the coordinate origin, and each is made of a circularly polarized (CP) metaline that shows a negative propagation phase constant at the design frequency (2.45 GHz). The antenna height is extremely small: approximately 0.03 wavelength. By changing the feed point, the antenna can be made to radiate a CP wave in each of the four orthogonal directions of the azimuth plane. The VSWR is less than 2. Mutual coupling between the four arms is small (less than -30 dB).

By controlling the surface reactance of impenetrable gradient metasurfaces it is possible to shape the phase front of reflected waves. This approach is similar to that used in conventional reflectarray antennas, where the phase of reflection from each array element is properly tuned. However, such phase-gradient reflectors always produce some parasitic scattering into unwanted directions. Here we present our recent results on non-local (spatially dispersive) gradient metasurfaces which do not have this drawback and demonstrate perfect anomalous reflection of incident plane waves into any desired direction.

This paper presents dielectric properties of air filled meta-atoms synthetic substrates fabricated in a single process using 3D printing. The permittivity and loss tangent of a given sized substrate can be changed by controlling the air infill volume fraction. Additive manufacturing (AM) technology constructs successive layers of materials to create three-dimensional (3D) objects. Traditional mechanical machining and micromachining is time costly and also generates material wastage. Moreover, it is difficult to create complicated internal structures using machining techniques in a single process. With AM, the final shape is successively constructed layer by layer and machining is not required. Therefore, there is no waste of materials for 3D printing and it is easy to generate complicated internal structures. 3D printed dielectric materials which are cost efficient and can be rapidly prototyped are becoming increasingly attractive in antenna design and fabrication.

We present a novel design procedure for shielded omega-bianisotropic metasurfaces (O-BMSs), fully reflecting a given incident plane wave into a desirable direction, without any spurious scattering. In previous work, we have proven that passive lossless O-BMSs can be designed to support any given field transformation that satisfies local power conservation. Recently, we have relied on this theorem to devise an accurate design of a perfectly-reflecting O-BMS in unbounded medium, harnessing auxiliary evanescent modes to match the intricate power profile formed by the interfering incident and reflected waves. Nonetheless, for many applications, such as radar cross-section reduction, a configuration in which the reflector is positioned near a perfect electrically conducting (PEC) surface is very common. In this paper, we propose a solution that fits this shielded configuration, utilizing auxiliary modes guided between the close-by PEC and the O-BMS to establish local power conservation, allowing a straightforward analytical design of perfect O-BMS reflectors.

We introduce non-reciprocal metasurfaces based on non-linear effects, allowing signal transmission from one direction to another, but not the other way around. We also present a particular design at THz frequencies, suitable for breaking reciprocity of wave reflection. Compared to other approaches for breaking reciprocity, non-linear metasurfaces have the significant advantage of not relying on any form of external bias and they can be used for the protection of sources or other sensitive equipment from strong external signals.

We present the recent progress in developing the mushroom and metasurface antennas for low-profile and broadband applications. The metamaterial-based mushroom antenna technology is first developed to realize broadband boresight-radiation with low profile on PCB and LTCC substrates operating from microwave to millimeter-wave bands. As a variation of the original mushroom antenna, via-less metasurface antennas are proposed along with miniaturization technique. Finally, the shorting-wall loaded mushroom antenna with new operating mechanism is reported as well.

At this conference, we will demonstrate how the bandwidth of vehicle-mounted electrically-small antennas operating in the VHF band can be improved while keeping the platform intact. In the example that we will present, a High Mobility Multipurpose Wheeled Vehicle acts as the main radiator and a meandered monopole antenna is used as a capacitive coupling element (CCE) to excite a desired set of characteristic modes of the platform. The size of the CCE is 0.06λ × 0.06λ × 0.06λ, where λ is the free-space wavelength at the frequency of operation, 60 MHz (ka ~ 0.47). The bandwidth of the vehicle-mounted VHF antenna is successfully enhanced by at least 400% using the proposed approach.

Eigenanalysis of canonically shaped structures served as an indispensable tool the conception and establishment of a plethora of electromagnetic structures from filters to cavities and antennas. However, the recent evolution of radio systems and wireless communications ask for the design of multifunctional rf front-ends in compact form and conformally integrated on mobile devices. The eigen-analysis features could again support this evolution but could only be performed numerically. It is toward this ambitions aim that our research effort is directed during the last years. This article presents an overview of the related work, which is based on finite difference, finite element and mode matching and moment method. The applications elaborated include closed as well open-radiating structures loaded with inhomogeneous and/or anisotropic media. Particular effort is devoted to external eigenmodes and characteristic modes, especially for antenna design.

The effects of introducing a phase-shift in the characteristic modes (CMs) of a rectangular conductive plane have been investigated. More in detail, a careful characteristic modes analysis (CMA) has been carried out in the aforementioned conditions to verify the possibility of significantly altering the shape of the overall radiated pattern. Among all the CMs, only two radiating modes (Jn) have been selected to achieve a pattern-reconfiguration ability. In particular, by a weighting linear superposition of only these two radiating modes over the conductive sheet, it is possible to realize a null-steering antenna in a principal plane. As proof of concept, a prototype of the proposed antenna has been realized and measured. The obtained results present a good agreement with the simulations and prove that the proposed design guidelines are reliable and also applicable to other kinds of structures.

In this work, we take a critical look at two practical antenna problems: (i) designing an antenna to provide the performance specified by the user; (ii) synthesizing the radiation pattern of a plurality of antennas mounted on a complex platform.

This paper describes a low-profile broadband 2×2 metasurface-based circularly polarized (CP) array antenna using a sequentially rotated series-parallel feed. The single element is a truncated corner square patch sandwiched between the ground plane and the metasurface of a lattice of 4×4 metal plates. These antennas are incorporated with the feeding network to achieve broadband operation. The 2×2 metasurface-based array antenna with an overall size of 64 mm × 64 mm × 2.34 mm (~1.17λo × 1.17λo × 0.043λo at 5.5 GHz) has a |S11| < −10 dB bandwidth of 4.56-6.98 GHz (41.94%) and 3-dB axial ratio bandwidth of 4.67-6.39 GHz (31.1%). The array antenna yields a broadside left-hand CP radiation with a peak gain of 11.6 dBic, a 3-dB gain bandwidth of 4.67-6.36 GHz (30.6%), and a radiation efficiency of > 88%.

This paper presents a rigorous analysis of the input impedance of a monopole antenna surrounded by a finite-height tensor impedance surface coating using the modal-expansion method. The tensor impedance surface is approximated by a thin anisotropic slab for facilitating the analysis. In addition, practical coaxial feedline was considered in the modeling. Based on the field expressions for all the sub-regions of the entire structure, the expansion coefficients can be determined by enforcing the tangential field continuity conditions across the boundaries in between adjacent sub-regions. The results calculated by the proposed approach are in a strong agreement with those obtained from commercial full-wave simulators. The proposed method provides a much faster solution and consumes less memory, making it highly useful for further exploration and optimization synthesis of integrated tensor impedance surface coated monopole antennas for a variety of applications.

Embroidery is an efficient method for the fabrication of textile antennas. We studied the effects of reducing the amount of conductive thread to achieve savings in material costs and the effects of the sewing pattern on the wireless performance of embroidered passive UHF RFID tags on two different fabric substrates. The antennas were sewed on cotton and polyamide fabrics, the ICs were attached to the embroidered antennas with a conductive adhesive, and the wireless performance of the ready-made textile RFID tags was evaluated through measurements. The fabric parameters were found to have a major effect on the tag performance. Based on our results, significant amounts of time and conductive yarn can be saved in the embroidery of RFID tag antennas by only partially sewing the tag antenna.

Improving the isolation between Multi-input Multi-output (MIMO) antenna elements in a mobile handset is a challenging topic in 5G communication time in order to achieve high data rate. Conventional decoupling methods for MIMO antennas are usually based on changing or neutralizing the interacted current, whereas the concept of controlling electromagnetic fields is seldom considered in the decoupling techniques. In this letter, a novel decoupling strategy is proposed for MIMO antennas in mobile handsets. The anisotropic non-resonant closed-rings metamaterials can be arranged in the space between antenna elements to re-shape the radiation pattern and to improve the isolation. As the proof of concept, a prototype of 8-element MIMO antennas is demonstrated. The simulation and experimental results indicate this decoupling method can improve the isolation to the 10 dB level at the limitation of 0.08-wavelength distance at sub-6GHz frequency range.

Non-destructive, real-time and in-situ measurement on cell apoptosis is highly desirable in cell biology. We propose here a design of terahertz (THz) metamaterial -based biosensor for meeting this requirement. This metamaterial consists of a planar array of five concentric subwavelength gold ring resonators on a 10μm-thick polyimide substrate. Both experiments and simulations show a very high sensitivity. Using this sensor, cancer cell treated with or without cisplatin is measured. We find a linear relation between cell apoptosis determined by Flow cytometry and the relative change of resonant frequencies of the metamaterial. This implies that we can determine the cell apoptosis in a label-free manner. An in-situ measurement scheme using reflective-type THz time-domain spectroscopy is also discussed. Therefore, our metamaterial-based biosensor can be developed into a cheap, non-destructive, real-time and in-situ detection tool, which is of significant impact on the study of cell biology. We think our work is a key step towards a real application of THz biosensor.

Link speed and code word length in spacecraft digital systems have a critical effect on equipment design in terms of operation and electromagnetic interference. In this work the behavior of a Low Voltage Differential Signaling / Spacewire link is evaluated through radiated as well as signal spectrum measurements. Various pulse frequencies and pattern lengths were tested and the results indicate that higher pulse frequencies increase the radiated emissions of the system. Radiated emissions are also affected by pattern length, due to the fact that the magnitude and the spacing of the spectral lines vary as the code word length increases.

This paper presents the design of a planar quasi- Yagi antenna capable of achieving high Front-to-Back ratio (i.e. FTBR > 34 dB), high realized gain (i.e. > 6.4 dBi) and relatively wide bandwidth (i.e. up to almost 1 GHz). This antenna is designed to cover the 2.45 GHz ISM band. The overall dimensions of the antenna are 69 X 64 X 1.575 mm 3. The antenna is made up of 5 director elements, 1 driven dipole and a reflector ground plane. Wide bandwidth is made possible through the strong coupling of the first director element and the driven dipole element. The antenna is optimized in order to achieve the above mentioned performance criteria. This antenna can be very useful for applications requiring highly directive radiation patterns such as point-to-point communications. The radiation characteristics of this antenna can be further enhanced by building a phased array based on it.

Cooperative diversity between satellite and terrestrial networks is an effective technique to increase the availability of satellite communications under fading conditions. The integration of satellite communications in 5th Generation mobile networks gives the advantage of a very high coverage area. However, the increased demand for bandwidth at backhaul links has led to the employment of millimeter wave frequencies, where the dominant fading mechanism is rain attenuation. In this paper, the end-to-end outage performance analysis of a satellite-terrestrial cooperative diversity system operating at frequencies above 10 GHz is presented, employing spatially correlated lognormal fading channels. The destination node (e.g. Base Station of 5G access network) combines the direct satellite link signal with a signal received through a terrestrial regenerative (decode-and-forward) relay using the Selection Combining technique. Extended numerical results present the impact of various operational, geometrical and geographical parameters on the system performance.

The radiation characteristics for a grid array antenna printed on a dielectric substrate (PGAA) excited in unbalanced mode (UnBal-PGAA) are analyzed using an integral equation with the method of moments (MoM). The UnBal-PGAA radiates a linearly polarized beam in the broadside direction. It is found that a difference in the excitation modes (balance and unbalance) does not affect remarkably the half-power beam-width and the frequency bandwidth of the gain.

Machine-to-Machine (M2M) networks have recently drawn significant attention as a result of the vast number of potential applications associated with them; however, consensus on the use of a standardized air interface protocol has not been reached yet. Due to their nature, M2M radio networks are expected to be densely populated and therefore prone to Multiple Access interference (MAI); in this paper, a radio interference evaluation framework is used to evaluate the performance of Impulse Radio Ultra Wideband (IR-UWB) as physical layer (PHY) for broadband M2M indoor networks. Considering an accurate channel model for the indoor environment, simulated results for the intra-network interference are presented. In order to obtain a realistic perspective of the system performance, different scenarios have been studied and the stochastic nature of both the network topology and the channel traffic have been taken into account. Finally, the use of a simple yet efficient power control scheme is proposed and evaluated yielding interesting results.

The paper considers the problems of the dielectric anisotropy and determination of the equivalent dielectric constant of different planar transmission lines on anisotropic substrates, when they have been covered with dielectric overlays with open or shielded surfaces. The idea is to investigate the possibilities for direct measurements of the equivalent dielectric constant for microstrip lines and coplanar waveguides by covering with thick enough dielectric overlay from the same material. A direct method has been proposed for determination of a set of three equivalent parameters of microwave substrates, applicable for accurate 3D design of MW planar structures.

The Wheeler Cap is the go-to solution for fast, broadband and accurate characterization of the radiation efficiency of compact antennas. Its ability to accurately measure high and medium levels of efficiency is well-documented; however, its capacity for detecting low levels of radiated power remained unknown. Starting from a highly-efficient, canonical antenna, this experimental study added increasing losses by means of precision fixed attenuators, thus creating a radiator with progressively lower, but tightly-controlled, efficiency. The recorded pairs of free-space and shielded measurements were treated by two independent post-processors. The results revealed that the Wheeler cap is capable of measuring very low efficiency levels at least down to -20 dB, or 1%; the worst case deviation from actual efficiency was 0.3~dB. Hence, the Wheeler cap becomes suitable for less common efficiency measurement scenarios, e.g., antennas immersed in lossy and dispersive materials.

In this paper, an alternative technique is proposed to miniaturize the Artificial Magnetic Conductors (AMC) unit cell. Novel unit cell achieves 60% surface size reduction at the same operating frequency compared to conventional mushroom-like unit cell. An AMC surface of 5×5 cells is designed under a dipole antenna with a distance of 0.05λ0, where λ0 denotes the free space wavelength at 0.9 GHz, for gain enhancement and radiation control. Both the dipole antenna and the AMC surface are fabricated and measured to demonstrate the potential of this new structure. At 0.92 GHz, a peak realized gain of 4.3 dBi of the antenna is achieved. The front-to-back ratio is under −15 dB and the maximum crosspolarization level, in the main beam, is less than −25 dB for both E and H plane. The simulated and the measured results are in good agreement.

Artificial Magnetic Conductors (AMCs) design and characterization in the UHF band is a big challenge while realizing low-profile antenna. In fact, AMCs unit cell often balance large geometries with high dielectric constants to achieve the desired frequency target while maintaining a minimal thickness. A compact AMC unit cell fabricated with low-cost FR4 substrate is proposed in this paper. Numerical technique is applied to simulate the behavior of the considered AMC and the conventional one based on mushroom-like unit cell. Two measurements methods in anechoic chamber have been compared to characterize the manufactured prototypes. Good agreement has been found between simulations and measurements.

In this paper, origami antennas are proposed for military field deployment. A high gain tetrahedron origami antenna (antenna #1) is introduced and then extended to circularly polarized antenna (antenna #2) for military satellite applications. Both the antennas are realized on paper substrate by using origami tetrahedron structure. The radiating aperture of antenna #1 comprises a triangular shaped monopole and two strip directors. The fabricated antenna #1 demonstrates a peak gain of 9.6dBi at 2.6 GHz with impedance bandwidth of 66% (2-4 GHz). The circular polarization characteristics of antenna #2 is achieved by exciting two identical triangular shaped monopole elements. Both the elements are fed by a T-junction divider with a phase difference of 90°. The 3-dB axial-ratio bandwidth and impedance bandwidth of the proposed antenna #2 are found to be 8% (3.415 to 3.7 GHz), and 70.2% (2.4 to 5 GHz), respectively.

A compressed sensing technique has been studied for accurate scatterer detection.It has many kinds of algorithms, and the features are different.In this paper, we evaluate the performance of compressed sensing algorithms for scatterer detection.We examine three algorithms, OMP, OIHT, and FISTA.We investigate the performance of the algorithms and it is concluded that FISTA reveals the best performance among the three algorithms.

Antenna gain is generally extracted from near-field measurements when the size of the measuring site (anechoic chamber or open area test site) does not meet the far-field constraints that include both distance and probe size limitation. Near-field measurements are usually performed by scanning the field on a closed surface around the antenna with a small size probe. In this paper, we show that the distance averaging method that we have previously proposed for gain evaluation in a multipath environment can also be employed for measurements in the near-field zone. We introduce an alternative technique to extract the gain by applying weighting functions on the near-field data when the size of the probe cannot be neglected compared to the wavelength. We validated our method by comparing the results to the gain measured at distances in the far-field region.

Chassis integrated antenna modules offer ten times the space of conventional automotive roof mounted antenna modules and can be fully concealed beneath the roofline. A pattern reconfigurable antenna for 2.6 GHz LTE is measured inside an automotive chassis module. The antenna can be electrically reconfigured to radiate towards the front, back, left or right side of the vehicle. Measurement results show that the antenna retains this ability when being hidden beneath the roof, proving that it is possible and feasible to hide antennas utilizing pattern diversity inside chassis modules.

Traditional circularly polarized (CP) horn antennas use a septum (or a partition) based feed, which is difficult to fabricate beyond 60 GHz. As an alternative, here we propose hexagonal waveguide based CP antenna design that is fabrication friendly and low-cost. Design, fabrication and characterization is shown for an F-band prototype. The prototype exhibits 18 dBi mid-band gain with 3-dB axial ratio bandwidth of 30%.

The paper studies two resource allocation strategies (GRID, anti-EMI) for multi-user OFDMA systems. These strategies are evaluated after being compared with the Round Robin and the FFR strategy in terms of mean throughput and mean dissipated power. All investigated strategies assign resources without Channel State Information (CSI), while both GRID and anti-EMI inherently combat Co-Channel Interference (CCI); hence they enhance mean throughput. Simulations indicate that GRID outperforms Round Robin and FFR in all scenarios into consideration and competes the anti-EMI strategy in various network orientations. The latter is justified especially for highly populated scenarios (i.e. 50% probability failure and 2 subcarriers per MT). As for the FFR strategy, simulations verify that the spectral efficiency is not the optimum, which fact has been already verified in the respective literature as well. Finally, the platform can inherently spare around the 70% of the maximum available power.

This paper designs and verifies the leaky wave antenna based on spoof surface plasmon modes with high radiation conversion within the entire operation bandwidth of 12-23 GHz. The conventional LWAs suffer from complexity of the design and low radiation performance at higher frequencies. Here we propose a method to design LWAs using symmetric spoof surface plasmon structures. Operating at the non-transmission frequency range, the SSP modes ensure the low transmitted power through the LWA and consequently do not require any loading termination and therefore, provide high radiation efficiency without any loading loss. Benefiting from a simple and single layer configuration, the symmetric plasmonic LWA generates high efficient backward, broadside and forward radiation with consistent performance through the entire frequency range. The design is experimentally evaluated and demonstrates its performance as a frequency beam scanning antenna.

Within the scope of this work, a reconfigurable antenna for automotive applications has been developed and constructed. The concept of planar parasitic array has been chosen due to its size. Furthermore, as an improvement to this concept, the parasitic elements were also used as active radiators. The antenna realizes four reconfigurable patterns that cover the angular regions in and against the driving direction as well as those orthogonal to the driving direction. Additionally a DC feeding network using metamaterials to decrease its influence on antenna characteristics is proposed. The measurement results match the simulated results and maximal gain of about 8.5 dBi is obtained.

In this paper multiple input multiple output (MIMO) channels are considered that are subject to tolerances. The deviations in amplitude and phase that occur at the transmitter and at the receiver are investigated. The resulting MIMO systems with different calibrations are evaluated in terms of the corresponding MIMO channel capacities and their suitability for beamforming-based evaluations as they are applied in e.g. communication over spatial multiplexing (SM) or direction of arrival (DOA) or direction of departure (DOD) estimation. The results reveal that some of the deviations have an impact on the evaluation of the channel capacity and on the beamforming (BF) but others are negligible because they are canceled during the processing. The negligible ones allow for savings in effort and computation both in MIMO channel determination systems like channel measurement systems and channel simulators and in communication systems.

In this paper, a novel low profile aperture-shared X/Ka-band dual-polarized antenna array is proposed for space-borne digital beamforming (DBF) synthetic aperture radar (SAR) applications. To begin with, the DBF concept and its operation mechanism for SAR system are discussed. In this work, every 2 × 2 Ka-band elements are combined as a subarray and connected to a channel while each one X-band element is connected to a channel. Then, a novel slot-antenna based on substrate-integrated-cavity (SIC) is proposed. The resonant frequency can be controlled by adjusting the length of the U-shaped slot. To share a same aperture, the X-band antenna is interlaced with the Ka-band subarray on the same plane. To verify the concept, an antenna operating at 9.6/35.75 GHz is designed, prototyped and tested. The results demonstrate good performance in terms of impedance matching, channel isolation, and cross polarization level. Such highly integrated low profile antenna can significantly reduce the potential cost of the DBF-SAR system.

Next generation 5G mobile architectures will take advantage of the millimeter-wave spectrum to deliver unprecedented bandwidth. Concurrently, there is a need to consolidate numerous disparate allocations into a single, multi-functional array. Existing arrays are either narrow-band, prohibitively expensive or cannot be scaled to these frequencies. In this paper, we present the first ultra-wideband millimeter-wave array to operate across the six 5G and ISM bands spanning 24-71 GHz. Critically, the array is realized using low-cost PCB. The design concept and optimized layout are presented, and fabrication and measurement considerations are discussed.

The use of magnetodielectric reconfigurable antennas on smartphones was investigated aiming to meet the requirements of the lower bands of current 4G standards and beyond. Since physical dimensions are constrained by the size of the mobile terminal, a reconfigurability mechanism based on partial magnetodielectric substrates and superstrates was studied in order to shift the resonance frequency lower while maintaining low system complexity. A printed inverted-F antenna (PIFA) was used to demonstrate continuous tuning, as opposed to the discrete tuning states of other methods, e.g., aperture tuning by means of switched capacitors. The numerical analysis of the PIFA started with lossy, isotropic ferrites, and then it elevated to gyromagnetic anisotropy. It was found that some of the benefits of tunable magnetodielectric loading are the ability to cover the 600-960 MHz band with just 3-5 sub-bands requiring realistic values of permeability, whereas an adequate radiation efficiency is maintained throughout the band.

In the millimeter-wave (mmWave) frequency band, radio frequency electromagnetic field (RF EMF) exposure is evaluated in terms of free space power density rather than the specific absorption rate (SAR) used in current cellular communications. In this study, we investigated RF EMF exposure of user equipment (UE) mock-ups employing a patch array operating at 15 GHz. Different understandings of maximum spatially-averaged power density to comply with different regulatory requirements are studied. Based on free space power density, the maximum permissible transmitted power (MPTP) of UE is calculated to compare the influence of different understandings. The analysis and results suggest that there is 1-2.6 dB MPTP difference for the ICNIRP limits and 0.1-1 dB MPTP difference for the proposed FCC limits depending on the varying compliance distance.

This paper presents a novel circularly polarized (CP) printed antenna with wide bandwidth and wide axial ratio (AR) beamwidth. The presented antenna is realized by bending a linearly polarized dipole into "S" shape with variable line width, which achieves circularly polarized radiation. Key parameters in designing such an "S" antenna are discussed and studied. It is found that this "S" antenna has some similar features to the linear polarized dipole, such as the feeding method, the radiation pattern in some main planes and nearly omnidirectional radiation in one main plane. To verify its performance, a ground plane backed inverted-S antenna is fabricated and characterized. Measured results confirm that the proposed antenna has good CP radiation, wide CP beamwidth within wide freqeuency band. The antenna is promising for applications in Global Navigation Satellite Systems (GNSS), and wideband wide-angle-scanning CP phased arrays.

This paper presents the pressure readout results from a piezoresistive pressure sensor in a biological environment mimicking the human head properties for intracranial pressure (ICP) monitoring application. The piezoresistive pressure sensor is powered wirelessly through inductively coupled antennas. After successful activation of the sensor, the pressure readout is demonstrated from 0 mmHg to 30 mmHg with a resolution of one mmHg.

The recently developed concept of two dimensional metamaterial - the metasurface, provides more convenient method to manipulate electromagnetic wave in a designable way within subwavelength distance. In this presentation we will firstly report the application of metasurface in focusing microwave in a dynamic and arbitrary way, which may be potentially used in the wireless electromagnetic power transfer to enhance the power receiving efficiency. Secondly, we will show the design examples of planar metasurface based absorbers that can efficiently harvest ambient RF energy.

A novel metamaterial surface with polarization-insensitive and wide-angle operating in a broadband is presented. The metamaterial cell consists of four same e-shaped Split-Ring Resonators (SRRs) arranged in rotating central symmetry. The structure is analyzed and optimized by using CST software. The harvesting efficiencies on the normal and oblique incidences, energy distribution and the S parameters are also investigated. The simulation results show that the maximum harvesting efficiency is 92% at 5.4 GHz with the HPBW (Half Power Beam Width) of 54% (4.7GHz-8.2GHz) for the random polarizations under the normal incidence. On the oblique incidence of 60o, the maximum efficiency is 98.2% and 57.6% for TM and TE modes, respectively. The meta-surface has been fabricated and measured to verify the effectiveness of the broadband, polarization-insensitive and wide-angle energy harvester.

In this talk, we discuss different aspects of realizing a smart contact lens as an example of a wearable wireless sensor enabled through the utilization of electromagnetic energy harvesting.

A coil is integrated inside an implanted antenna in order to support inductive charging. The implanted antenna has been designed for wireless data telemetry at 400MHz region and radiating wireless charging at 915MHz. The antenna-coil system is embedded into a three layer canonical model of human arm. In the inductive charging case an external transmitting coil is considered while in the radiating charging scenario a dipole is implemented. Several simulations are carried out for the antenna-coil system. While radiating charging seems to be more efficient inductive charging can be used as a complimentary solution since they both can coexist.

The emerging roadmap for active medical implant devices includes two distinct types of particularly challenging applications that will require the introduction of new antenna and communication technologies. On one hand, there is continued demand for the miniaturization of wireless implants. The quest for more compact solutions is generally application specific, for example, the miniaturization of a swallowable lab-on-a-chip that can detect cancer bio-signatures in the gut and relay an instant result to the user's mobile phone via Bluetooth. In this case integrated mechanical and antenna design can be employed to create a practicable solution in an appropriate form-factor, especially considering that other limiting factors such as battery requirements are more relaxed. Therefore, there remains a need for generalized, application agnostic, advances in implant antenna design. On the other hand, there is the emergence of interest in intra-body networks (IBNs) where two or more implanted devices co-operate for clinical advantage.

A wearable antenna with tripolarization diversity is designed in the 2.4 GHz band. An inductive loaded circular monopolar patch with a microstrip annular ring are combined to realize the tripolarization. Simulated and measured results yield a sufficient bandwidth for WBAN. The port isolation reaches 13.5 dB, and the correlation coefficients indicate a good diversity.

The number of applications using body-centric communication has undergone a tremendous growth since the early years 2000, and the increase has been even more marked in the past three four years. These applications require In-, On-, or Off-Body communication links, and comprise among others fashion, sports, military, security and healthcare. In this contribution design rules for the design of antennas for wearable or implantable systems are addressed, with the aim of maximizing the radiation efficiency of the antenna-phantom system while minimizing the specific absorption rate in the phantom.

This paper reviews a novel kind of antennas called planar aperture antennas which have recently been developed by State Key Laboratory of Millimeter Waves, City University of Hong Kong. Compared with conventional aperture antennas, such as horn and reflector antennas, planar aperture antennas maintain high gain and wide bandwidth, but have a much lower profile with only one quarter-wavelength height. Since the height at mmWave band is as low as most of commercially available laminates, planar aperture antenna can be realized at very low cost at the mmWave band.

In this paper, a wideband linearly polarization (LP) stacked patch antenna with two switchable feeding ports is proposed. Individual excitation at the two diagonal ports can produce a 180-degree phase-shifting due to the symmetrical structure. Then, a polarization reconfigurable antenna array based on the proposed LP antenna is developed, which can radiate vertical-LP (V-LP), horizontal-LP (H-LP), left-hand circular polarization (LHCP) and right-hand circular polarization (RHCP) waves by properly selecting the feeding ports.

A wideband horizontally polarized (HP) omnidirectional antenna is presented. The tightly coupled array (TCA) mechanism is ultilized into the design of the antenna to realize reduced lower cut-off frequency and improved bandwidth. The -10dB impedance bandwidth is 102.6% from 4.8GHz to 14.7GHz. Meanwhile, uniform omnidirectional radiation patterns with a gain variation of less than 3dB are obtained within the frequency band of 4.7-8GHz (51.96%).

In this paper, two miniaturized antenna elements working in the high- and low-frequency bands respectively are proposed firstly. Then, several kinds of subarray arrangements and decoupling techniques are demonstrated explicitly. Finally, three types of multi-array multi-band antennas with good performances are presented to meet the practical base-station applications.

We present a novel ultra-wideband (UWB) dual-linear polarized phased array designed for simultaneous transmit and receive (STAR) monostatic antenna systems. The dual-linear polarized array employs a tightly coupled dipole topology that achieves an UWB operation from 2GHz to 18GHz, viz 9:1 bandwidth. Also, its port to port isolation is at least 45dB at broadside. The array consists of tightly coupled dipoles that are integrated with a folded Marchand balun. The latter serves as a balanced feed to a 50Ω source. One of the array polarizations is used for transmission and the other for reception. To improve scanning performance, the traditional dielectric superstrate is replaced with a frequency selective surface. Notably, the proposed tightly coupled dipole array (TCDA) scans down to 60o in both E and H planes with a port to port isolation of at least 35dB across the entire 9:1 band.

We present a monolithic, butterfly-shaped double-slot antenna architecture with dual-mode feed structure that concurrently supports common- and differential-modes with high isolation. The novel antenna structure is used as a balun-free differential-mode generator with high common-mode rejection ratio and enables non-contact on-wafer characterization of mmW/THz frequency differential circuits for first time.

After graphene was first isolated from graphite, it has attracted a lot of research interest because of its extraordinary mechanical, thermal, chemical, electronic, and optical properties. Especially since Hanson published his investigation of the interaction of an electromagnetic current source and electrically or magnetically biased graphene at the interface between two materials, thousands of journal and conference papers have been published on antennas based on graphene. This literature includes various graphene based antennas, e.g., patch antennas, dipoles, leaky-wave especially at THz frequencies. However, in practice there are many limitations: antennas, reflect arrays, high-impedance surfaces, and related devices for microwave, millimeter-wave and THz frequencies. Indeed, theoretically the use of graphene in antennas promises miniaturization of the antenna and tunability of the resonance frequency and input impedance, high loss of the TM polarized surface wave enabling the miniaturization, high electric or magnetic field needed for biasing, very high Young's modulus (~1 TPa) making MEMS switches or capacitors impossible, etc.

In this work, a novel design and fabrication procedure for realizing 3D Luneburg lens using additive manufacturing technique is developed.The required continuously varying relative permittivity profile is realized by controlling the filling ratio of a polymer / air based unit cell. Compared to conventional manufacturing techniques, this 3D printing approach is much more convenient, fast, inexpensive and capable of implementing Luneburg lenses in the millimeter wave range. By mounting feeding elements on the lens surface, high performance electronically beam scanning array can be implemented for automotive radar application.

In this contribution, we will present the design and fabrication of planar antennas based on periodic surfaces for use in mm-wave and low-THz communication and radar systems. Micromachining processes will be discussed and the design of the proposed antennas based on the capabilities as well as tolerances of these processes will be presented. The analysis techniques employed for multiple periodic surfaces and the resulting antennas will also be described.

This manuscript proposes the combination of several photomixing THz sources for overcoming the power limitations of this technology. Each element is placed in the gap of a balanced antenna. All the elements conform a 2D rectangular array. For avoiding issues related to having out-of-focus sources when using one electrically large silicon lens, two different strategies are considered: increasing the density of elements by using a compact design and using an array of dielectric rod waveguide antennas instead of the lens. Experimental considerations are also provided for two prototypes manufactured in the 1550 nm window. Measured power level will be shown at the conference.

Phase-change materials and in particularly vanadium dioxide have recently been reported to provide a suitable mechanism for fast switching related to reconfigurable antennas. This paper describes two such reconfigurable antennas where a very small and thin film of phase change material was used to alter the antennas resonant frequency. Simulated and measured results from two fabricated prototypes are presented. The integration challenges and the future applications of vanadium dioxide will be discussed.

Theoretical limitations on shielding and reflective properties of a thin passive microwave magneto-dielectric metamaterial absorber layer that follow solely from the boundary conditions were numerically investigated using well-known expressions for reflection and transmission coefficients of a plane half-space or an infinite plane sheet of a magneto-dielectric.

In recent years, electromagnetic interference (EMI) of an implanted cardiac pacemaker (PM) has been investigated. However, there are few studies of specific absorption rate (SAR) around the PM by the mobile radio terminal. In this paper, SAR due to a wireless radio terminal which has high resolution source model is calculated. As a result of calculations, SAR at 2 GHz was 4 times higher than that at 900 MHz because of reflection wave at PM housing. However, all calculated SARs were below the international safety guidelines.

Biological medium surrounding an implanted device is characterized by a high dielectric permittivity and a loss factor. This fact results in a degradation of the electromagnetic signal by a strong wave reflection from the interface and refraction phenomena accompanied by the total internal reflection at the interface between the biological tissue and the air. A miniature dipole antenna with SAW resonator was suggested and realized for wireless remote temperature monitoring. Results of modeling and experimental investigations of electromagnetic waves propagating over the surface of a human body are also discussed. The results numerical simulations of wave propagation parameters such as attenuation and phase velocity of the waves on the plane and curved surfaces are confirmed by measured data. Some examples of printed antennas for near field and far field implementation are considered.

A low-profile electromagnetic band-gap enabled textile wearable antenna covering the spectrum between the 2.36 and 2.40 GHz of the new released medical wireless body networks (MBANs), is presented. The integrated EBG with the proposed antenna reduces the radiation intensity into the human tissues around 13 dB; and also decreases the effect of frequency detuning. The antenna structure is compact size with total volume of 54 × 54 × 3.1 mm3. It offers 8.5% impedance bandwidth and a power gain of 6.79 dBi. Specific absorption rate (SAR) evaluation is also carried out to validate the performance of the antenna when it is placed closely to human body. The antenna size and its ultimate performances could be selected as a good candidate for integration into various wearable devices.

The capability of controlling the spatial distribution of a field into a given scenario is relevant to many applications as different as hyperthermia treatment planning and wireless network optimization. In this respect, many strategies to focus the field into a target point have been presented, whereas the possibility of arbitrarily shaping a field still remains an open challenge. In this communication, we present an innovative approach to field intensity shaping that unravels the original NP hard problem into several convex programming ones, by means of the proper equality constrained method. The approach is discussed and assessed with a numerical example.

This paper presents measurements and simulations for small helical coils coils that provide inductive power transfer for implanted medical devices (IMDs) in sub-GHz region. In such context, the coils need be very small to be implanted within devices, or even to be used as an alternate solution combined with UHF antennas. The influence of the body and the mandatory small size of the coils bring technological challenges concerning efficiency and measurements accuracy which must validate our simulations. In this paper, a deembedding technique is used to take into account the dedicated test fixture, and further work will investigate the electromagnetic influence of a liquid phantom, modeling the muscle tissue.

In this paper, we elaborate a reference antenna in terms of direction of arrival (DOA) estimation accuracy to verify its reliability under realistic propagation conditions. Estimation accuracy decreases for the reference antenna due to environmental influences. Our main contribution is modeling such non-anechoic environment in the simulation by considering proximity to earth with surface roughness, antenna cover against climatic influences and height of the stacked-up system over earth in a real-world deployment. We developed a ring extension for the antenna, such environmental influences are minimized and the DOA estimation accuracy is improved again. The overall localization performance of a system with several DOA estimation sensor nodes for different antenna configurations is proven in a simulation environment. The results show an improvement of the localization accuracy for the optimized antenna.

We present an arbitrary-shaped patch antenna design procedure. The design technique is based on a variant of Biogeography Based Optimization (BBO) algorithm. In this paper, we apply Opposition-Based Learning (OBL) concepts for antenna design. More specifically, we use a new Modified Biogeography Based Optimization (BBO) algorithm enhanced with OBL techniques. The preliminary results of the proposed method indicate the advantages and applicability of our approach.

in this paper a dual polarized antenna array with shaped beam for outdoor WiFi access points, e.g. hotspots operating at the upper WiFi frequency band of 5.8 GHz is described. The aperture is composed of 64 waveguide antenna elements. By controlling the amplitude and the phase of only 24 elements, a shaping of the pattern in the main beam is achieved. Both polarisations are also excited by each antenna element. The presented base station array has therefore a broad half power beamwidth allowing for an easy alignment/installation of the base stations in the field. Last but not least, it shows low correlation factors which mean that it can be also used for MIMO antenna systems.

This paper presents an aerosol jet printed end-fire antenna operating at 24 GHz on a 3-D printed substrate for the first time. A compact sized quasi-Yagi-Uda antenna is chosen to achieve end-fire radiation pattern, and is optimized to be directly fed by a 50 Ohms microstrip transmission line with a balun. The partially metalized substrate serves as the ground as well as the reflector for the antenna. Additionally, a cavity is integrated in the back of the substrate to provide low loss. The simulated performance shows 26.4 dB return loss at 24 GHz, 3.32 dBi of peak gain and 57.7% radiation efficiency. The measurement are carried out over a frequency shows the return loss of 28.9 dB at 27.8 GHz. The combination of aerosol jet printing and 3-D Polyjet printing processes in this paper demonstrates a good advantage of additive manufacturing technology, which allows for highly efficient fabrication of low-profile antenna and other novel RF circuits.

We present a fully planar, easy to fabricate antenna for millimeter-wave communications, based on a new substrate-integrated waveguide (SIW). The SIW itself is entirely planar, since it is designed using series of side-by-side complementary split-ring resonators (CSRR), instead of vias, with the CSRR being etched on top and bottom metal ground surfaces that cover the dielectric substrate. This metamaterial-inspired structure provides a single-negative effective material parameter behavior that blocks wave propagation to the perpendicular direction. Hence, two parallel structures of this kind can be used to design an SIW, with propagation losses comparable to the conventional one. The antenna structure is consequently designed, by the use of proper cavities within the substrate and radiating slots on the ground structure and provides an easy to fabricate alternative for millimeter-wave and 5G communications.

The goal of this paper is to investigate the performance of MIMO-WCDMA networks, where Principal Component Analysis (PCA) is employed at the reception. Multipath propagation is exploited, as the individual received signals can be seen as different instances of the same physical phenomenon (i.e. transmission and reception of WCDMA sequences). In this context, the number of eigenvectors and eigenvalues for accurate signal reconstruction is first defined. Afterwards, the constructed covariance matrix is used in order to reduce the overall complexity of a proposed transmission strategy for signal transmission in MIMO-WCDMA networks in diversity combining transmission mode. As results indicate, for a 2x2 MIMO orientation (i.e. two transmit and receive antennas) and six multipath components, the complexity of the proposed algorithm can be reduced up to 15%/60% for SNR equal to 0/5 dB, respectively.

In this paper we investigate the influence of dielectric and magnetic losses of an Epoxy bonded Yttrium Iron Garnet (YIG-Epoxy) composite substrate on the performance of a reconfigurable microstrip patch antenna. The antenna under investigation is a microstrip patch antenna printed on a 60/40 w/w% YIG-Epoxy composite substrate and controlled by an externally applied DC magnetic field. It is observed that high dielectric losses of the composite substrate can dramatically deteriorate the radiation efficiency of the proposed antenna in the demagnetized state, while in the magnetized state the magnitude of the resonance linewidth (ΔΗ) of the composite substrate is the main parameter responsible for the reduction or improvement of the radiation efficiency. Considerable effort has been made to fabricate a YIG-Epoxy substrate with improved properties regarding dielectric loss tangent and magnetic resonance linewidth. The prototyping and characterization of a reconfigurable patch antenna on the "improved" YIG-Epoxy substrate is also presented.

This paper presents an air-cavity-fed four-element slot antenna array, which is fabricated using a modified silicon micromachining process. Different from traditional silicon micromachining process, the silicon dielectric is fully plated with gold, and the electromagnetic wave cannot touch the silicon directly. In this modified silicon micromachining process, air cavities can be easily obtained to avoid substrate loss, with the merit of low loss. This new silicon micromachining process is recently introduced to the millimeter-wave antenna design, with the basic procedures of through-silicon-wafer dry etching and gold plating. An example of a four-element slot antenna array is constructed, characterized, and tested at 60 GHz. The proposed slot array is inspired by breaking the field symmetry of the channelized coplanar waveguide. By alternatively and periodically arranging the shielding blocks, a four-element slot array is achieved and fed by an air cavity, which is easily achieved using the modified process.

This letter presents a new design of an ultra-wideband Elliptical Antipodal Vivaldi antenna with elliptical tapered slot edge and circular loads. A new empirical formula for the ground structure was proposed for ease of design. The fabricated prototype has proven better low cut-off frequency performance in term of return loss, gain and radiation pattern throughout a bandwidth from 730 MHz to over 20 GHz with good radiation characteristics.

An indirect impedance measurement approach that does not require direct cable attachment or large space using a two-port network is presented. Using a straight wire monopole as an interrogating antenna and measured impedances of three calibration standards, the input impedance of a small spherical helix dipole over a ground plane is retrieved. It is found that accurate result is obtained around the dipole resonance frequency. The accuracy and sources of error are discussed.

In this contribution, a combined electric field/magnetic field surface/volume integral equation approach is presented with special features for the characterization of substrate integrated waveguide (SIW) components. Due to the use of a parallel plate waveguide Green's function, only a small number of volume current basis functions are necessary to model the SIWs. The focal point is set on the specification of microstrip line-SIW transitions using a via and a pad/antipad configuration for the coupling between the microstrip parts and the SIW. An effective S-parameter extraction is used with both microstripand special SIW-waveguide ports. The main goal comprises the design of cheap broadband transitions to SIWs with a thick substrate suited for the feeding of a new class of compact endfire SIW-antennas.

The technique of using multiple feeding points on a patch antenna in order to achieve improved bandwidth performance, is here exploited to feed a supershape structured radiator. The achieved operating bandwidth (from 2.5 to 3.9 GHz) is an important advance compared to the performance of the worn out, single fed and regularly shaped patch antennas. The proposed antenna operates from 2.5 to 3.9 GHz with linear polarization and its behavior is verified in terms of Return Loss, VSWR, input impedance, radiation pattern, electric field and efficiency.

The unified asymptotic theory provides an accurate description of the field dynamics in (chirped) dispersive electromagnetic pulse propagation of arbitrary initial width in causally dispersive media. The propagated field is a superposition of pulse components whose characteristics are directly related to the dynamical evolution of the saddle points that are relevant in the asymptotic analysis. Here, this theoretical approach is utilized in order to investigate the dependence of the temporal width of the propagated field's envelope on the input field and medium parameters from the sub-cycle to the quasimonochromatic initial pulse regimes.

Cherenkov radiation (CR) is electromagnetic radiation emitted by a moving charge passing through a dielectric medium at a speed greater than the phase velocity of light in that medium. However, even with the help of these novel materials, there still exists a speed threshold of charged particle to generate CR and the electron energy is larger than 25keV. Here we propose a new approach to eliminate the electron speed threshold to generate CR and report the first on-chip integrated CR ultraviolet source. Having electrons fly on the surface of hyperbolic metamaterial, it is predicted that CR could be obtained with no electron speed threshold. By integrating a planar electron emitter on multi-layer metamaterial, we simulated the CR generation from 70nm to 500nm even when electron energy is as low as 1kev. This work opens up the possibility of on-chip integrated optoelectronic devices by making use of CR and studying the interaction of flying electrons with artificial nanostructures on chip.

A Passive Multi-beam Antenna Systems with beam forming technology that can be used to increase quality of service, network capacity, and spectrum to meet the current and future demand of data usage and network capacity is presented. The system presented can produce as many as 32 narrow high-gain beams in a 120° sector with beam crossing set to be between 3 to 10 dB. Each beam provides a capacity and throughput multiplication over a traditional cell site. Frequencies can be reused in a sector resulting in a spectrum multiplication of as many as 32 times. With the use of multiplexers several channels can be combined and transmitted in each beam providing multiband/ multi-channel transmission with a single antenna system to further increase user capacity and throughput

This paper proposes the horizontally polarized omni-directional antenna with cylindrical frequency selective surface (FSS). The FSS features the orthogonal polarization conversion function. Therefore, the vertically polarized wave radiated from a dipole antenna is converted to the horizontally polarized transmitted one. The simulation results show that this antenna has the good performance as the horizontally polarized omni-directional antenna.

This paper proposes a novel multi-stub ultra-wide band planar monopole antenna. The radiation patch of the antenna is composed of a pair of back-to-back E-shape-like patches. The E-shape-like patch is the extension of the E-shape patch, adding two semi-circle units at the back of the E-shape patch and extending the top of the E-shape patch with an inverted L-shape patch with a "suspending hammer" unit. Two semi-circle slots etched on the rectangular ground which is extended making the ground with two step-like structures to realize ultra-wide band. The antenna is printed on a substrate of the dielectric constant 4.6. The experiment results show that the bandwidth of the antenna is 3.2GHz-18.7GHz for S11≤-10dB.

Metamaterial particles are essentially electrically-small radiators with polarization dependency. Previous works on metamaterials were concerned primarily with using such particles to achieve homogeneous media that enabled unconventional propagation. The metamaterial radiators are inefficient if used in isolation, however, if used as an ensemble, they, collectively, radiate efficiently. This suggests their use as antennas. Because of their electrically-small size, metamaterial elements can be considered as Huygens radiators. With this perspective, a systematic procedure for designing directional and efficient antennas can be developed as we demonstrate here. Furthermore, the new perspective and technology can provide conformable antennas for non-planar platforms.

In this paper, we develop a novel technique for computing the complex-conjugate zeros of rational transfer functions in partial fraction form, by searching the complex Laplace $s$-plane for the local minima of the determinant of a block matrix derived from the state-space equations. A higher resolution scan, in the vicinity of each local minima, may be used to increase precision of the zeros. A numerical example is used to illustrate the efficiency and effectiveness of the proposed method.

Driver safety, traffic efficiency and green transportation can be significantly improved by Truck-to-Truck (T2T) communications. This paper proposes a 5.9GHz Electronically Switched Parasitic Array Radiator (ESPAR) antenna that employs three printed monopoles as array elements. The antenna demonstrates a reconfigurable radiation pattern and compact dimensions that make it ideal for installing it in the side mirrors of a heavy duty vehicle (truck). By adjusting the voltage supply of two PIN diode switches, the antenna can function in three different operating states and provide three different patterns (one quasi-omni, two directive beams) to the T2T link user. An ESPAR antenna prototype is manufactured and experimentally characterized, demonstrating a good agreement between the simulation and the experimental results. The proposed antenna exhibits a satisfying impedance matching and a considerable gain enhancement in two opposite directions when the antenna operates in the directive mode. An interesting investigation is also performed on the exact position of the antenna inside the truck side mirror.

In recent years, various types of medical applications of microwave antennas have widely been investigated. Typical recent applications include medical information transmission, diagnosis, and treatment. In this paper, microwave techniques for treatment, which employ thermal effect of electromagnetic wave, are introduced. They are thermal treatment of cancer called hyperthermia and surgical devices using high power microwave energy. Here, in order to evaluate characteristics of the devices, numerical calculation is introduced. In addition, experiences of animal experiment and clinical treatments using our developed antennas are also presented.

Practical as well as theoretical aspects of medical microwave imaging require short antennas with short impulse response function for transmission and reception of the sounding fields. Since usually antenna design goals are targeted to good feed point matching, one runs into unsolvable problems in case of wideband measurements. The paper will introduce a radar channel model based on electrically short antennas and it will discuss how to circumvent the mismatch problems.

The design of optimal microwave exposure systems for medical applications - in terms of number of elements and/or achievable performances - requires to update the microwave engineer's toolbox, not only to reduce the complexity and the cost of the systems, but also, and more important, to develop devices capable to ensure the effectiveness of the treatment or the accuracy of the diagnosis. Recently, the authors of this communication have proposed a novel framework to design phased arrays in medical applications, which, to the best of our knowledge, represents the first systematic attempt to envisage such an updated toolbox. At the conference, we will review the main aspects of this new design framework and discuss its implementation to some diagnostic applications.

The main objective of this study is to assess whether two parallel metallic plates implanted in human could be expected to cause electromagnetic coupling enhancements to external radio frequency electromagnetic fields from the viewpoint of human safety. In this report, numerical analysis for a human with metallic plates embedded in the head exposed to radio waves is described. The dependency of electromagnetic coupling on the metallic plate modeling is investigated using the near field of a half-wavelength dipole antenna at 2 GHz based on localized specific absorption rate values, in which osteosynthesis plates of mandibular fractures are implanted. Some papers regarding interaction of RF EMF and metallic implants have been published. Our study focuses upon the coupling enhancement due to combination of two metallic implants aligned in parallel.

Compact, wideband and unidirectional loop antennas are presented, that are based on a conventional planar loop antenna that is loaded in a mu- negative (MNG) fashion with series capacitors, enabling a mu-zero (MZR) resonance to be excited. This, together with the inherent loop resonance and a third resonance introduced by a director element, result in a wide impedance bandwidth and enhanced directivity. Two variants of the MNG-loaded loop antenna are presented; one with a uniform distribution of the MNG-unit cells, and one with a non-uniform distribution. It is shown that both antennas, which have a compact size, achieve a wide operating bandwidth in excess of 50% in the range of 0.6 to 1.1 GHz in the lower UHF band. The uniformly loaded antenna has a measured gain of 3.2 dBi, while the non-uniformly loaded antenna has a higher measured gain of 4.8 dBi. Both antennas have high front-to-back ratios in the range of 10 dB throughout the operating band.

This paper presents a beam switched antenna attachment for mobile handset terminals. This attachment provides a satellite communication link in case of emergency or in the area not covered by cellular systems. This paper presents a prototype antenna with a simple feeding circuit, providing two beam patterns switched in two directions. Switched pattern is also demonstrated by measurement.

At first, an AMC substrate composed of a capacitance grid and a metal plate is proposed to thin its thickness. Then an AMC inspired small antenna composed of a dipole antenna and a small AMC substrate, named MACKEY, will be proposed. It will be shown that MACKEY works not only in free space but also on a metal plate. Further, dual band / multi band design of MACKEY will be proposed.

A sleeve antenna has been employed for experiment because of its simple structure. The sleeve antenna is required broadband and easy producing structure. In this paper, the volumetric sleeve dipole antenna is designed to confirm the effect of the parasitic element. The current distributions are calculated to explain the principle of the parasitic element. The nulls of the radiation pattern in the high frequency is reduced by added metal plate on the tip of the inner conductor. The planar sleeve antenna is also designed to produce easily. The antenna works broadband. The nulls of the radiation pattern in the high frequency is reduced.

The human body's absorption of electromagnetic fields from communication enabled devices has consistently been a research topic for both researchers from universities and companies in the mobile communication industry. The absorption of electromagnetic fields could mainly result in two consequences: (a) antenna radiation efficiency of the device could deteriorate dramatically; and (b) a large amount of the radiated power could be dissipated into the human body, such as the hand, ear, scalp and brain, which is defined and described by Specific Absorption Rate (SAR). A comprehensive analysis of electromagnetic field absorption by the human body has been carried out to explain and answer some of the key questions in this area.

In this paper, a novel low-profile circularly polarized crossed dipole antenna operating at UHF band, with small dimensions of 180 mm 160 mm 4 mm ( 0.22λ 0.20λ 0.005λ ) is proposed. Meandering lines are designed to reduce the size of the antenna. To achieve circularly polarized radiation pattern, a feeding network composed of a power divider and 90o phase shifter is used. Besides, the ground of the feeding network serves as a half-ground for the radiation part. Finally, the antenna is modeled as the optimized version. It has good simulated realized gain with radiation efficiency about 80% to 90% at resonant frequency.

There are many different frequency bands above 6 GHz and into the mm-wave range above 30 GHz that are possible candidates for use in future 5G cellular systems. In this paper, we present some results for wireless channels at 15 and 28 GHz in an indoor scenario. The results are based on both measurements and ray tracing simulations. Basic comparisons of measured and simulated power-delay profiles, angle of departure and received power are presented to give an insight to the possibilities and limitations of utilizing ray tracing to characterize the indoor wireless channel at 15 and 28 GHz. We show that it is important to consider human body shadowing as well as finer structures and details in the ray tracing environment model in order to achieve reasonable results. Lastly, we also perform ray tracing simulations to assess the performance of a number of different array signal processing techniques, including beam- forming, hybrid beamforming and spatial multiplexing.

Beam-switching/scanning antenna arrays have received more and more attention in recent years owing to the rapid evolution of modern mobile systems such as the 4G/LTE and next-generation 5G wireless communication. The radiation beam/null of the switching antenna array can be adaptively steered in a prescribed manner to achieve better immunity against interference and hence higher data throughput. A beam-switching/scanning array can be realized using either analog or digital beamforming networks. In this presentation, we are going to present two new configurations for realizing beam-switching/scanning arrays. The first one is a variation of the conventional retrodirective array (RDA). The common formulae for realizing a retrodirective array are revisited and generalized to fulfill a retro/reflecto-scanning array. The second part covers a new variation of the conventional Butler matrix using reconfigurable synthesized transmission lines as 1-bit phase shifters. The design details of both arrays will be introduced during the presentation.

We present an innovative capacity optimized antenna design strategy that we call antenna synthesis. The methods focus on the synthesis of antenna radiation patterns that are optimized in terms of mutual information, taking into account the specific limitations of the antenna design, such as the available space (for the antenna structure), frequency, polarization, number and arrangement of the antennas. The optimization focuses on volume based channel knowledge and on the theory of the intrinsic capacity. Based on this we developed algorithms that allow to determine optimized fixed radiation patterns also for time-variant channels. The antenna synthesis is applied to simulated and measured mobile MIMO multipath propagation channels.

Smart antenna is the key technology for Satellite communications On The Move (SOTM) because it can increase the channel capacity, coverage range and flexibility of the communication systems. Firstly, this paper presents a brief review of the state-of-art development on antennas for SOTM applications, and different types of smart antenna for SOTM are discussed. Then, the paper presents two recent examples of smart antennas developed by the team at the University of Kent in collaboration with their partners. One is a low-profile wide-angle electronically beam scanning smart antenna system for Ka-band SOTM. One important feature of this antenna is that it has a planar structure and can achieve wide-angle electronically beam scanning. Another design example is a Ku-band low cost dual polarized reconfigurable reflectarray with 1-bit phase control by using PIN diodes. Both examples achieved good performance of beam scanning and measurement results are given. A conclusion is given

In this paper, several two-dimensional multibeam antennas are presented based on the compact substrate integrated waveguide (SIW) twist technology. Firstly, four 90° couplers and four 90° SIW twists are combined to feed a 2×2 multibeam integrated antenna array. Simulated and measured results show that the gain of the antenna is larger than 8.5 dBi. The antenna beam scans at different angles in the two-dimensional plane excited at different ports. Then, a sixteen-beam two-dimensional multibeam antenna array is designed based on the 4×4 Butler matrix. Such a beamforming network (BFN) includes eight SIW Butler matrices and sixteen 90° SIW twists. Integrated with sixteen antipodal linearly tapered slot antennas (ALTSAs), several beams with different directions can be generated.

We proposed an anisotropic metasurface performing different scattering properties depending on the polarization of the incident electromagnetic wave. The proposed metasurface is composed of orthogonally I-shaped structures with a thickness of only 0.067 working wavelength, and the reflection phase for certain linearly polarized incidence can be independently controlled by tuning the corresponding geometric parameters. Based on this principle we designed a bi-functional metasurface for differently polarized wave. It can behave as a phase-compensation planar reflector to transform the primary out-phase radiation from an x-polarized feeding antenna into a secondary planar wavefront with high directivity reaching 22 dBi. On the other hand, it behaves as a diffuse reflector composed of randomly distributed reflection phases to suppress the backward radar cross section in a broad band (8.2 GHz- 12.5 GHz) under the illumination of y-polarized incident wave.

Arbitrary-length zero-degree phase-shifting lines are presented at X-band that are based on negative-refractive-index transmission-line (NRI-TL) metamaterials implemented in substrate integrated coaxial line (SICL) technology. Initially, a host substrate integrated coaxial line was loaded with a series interdigital capacitor and shunt printed inductors to form a single NRI-TL metamaterial unit cell. Subsequently, multi-stage NRI-TL metamaterial lines were realized by cascading multiple NRI-TL metamaterial unit cells. The performance of the metamaterial lines is analyzed based on their reflection loss, insertion loss, radiation loss and insertion phase for different lengths of line ranging from λ/5 to λ at 10 GHz. It is shown that the radiation loss remains below 0.003% of the total losses for all presented lengths of metamaterial lines, while exhibiting good reflection and transmission characteristics. These results indicate that the proposed zero-phase NRI-TL metamaterial lines in SICL technology are well suited for very low-loss guided-wave applications.

A smartwatch antenna with a novel high impedance surface (HIS) is investigated in this paper. In order to fit the all-metal smartwatch applications, a non-planar HIS is proposed instead of using a traditional planar one. With the presence of the HIS, the wrist phantom has a slight impact on the antenna's performance and a low SAR can also be obtained. The antenna can achieve a gain of >1.3 dBi and an efficiency of >40% from 2.4 to 2.484 GHz even when it is mounted above a wrist phantom. Hence, it can work effectively for WIFI or Bluetooth system.

The estimation of the proper amplitude and phase excitation of phased array antennas network used for hyperthermia treatment constitutes the scope of this work. The aim of this array is to focus the electromagnetic power only on the malignant biological tissues and not to create other unwanted secondary "hot spots". The proposed method is based on the reciprocity theorem in order to build the simulation model for the exact numerical calculation of the excitation values. Explicitly, a simplistic body model or Human arm is constructed including the antennas and the water bolus utilized for cooling. An antenna is placed at the tumor center acting as source and an electromagnetic simulation is performed to estimate the path delay (phase difference) to each antenna array element. These delays or phase differences are used to define the array excitation currents ensuring focusing on the tumors.

This paper shows the analysis of a typical Printed Circuit Board (PCB) Split Ring Resonator (SRR) Electrically Small Antenna (ESA) based on lumped circuit model. Having technical limitations such as 5 mils copper trace width and trace separation of 3.5 mils, it inherently lacks sufficient resistance to operate efficiently. Through a series of different SRR configurations, this can be improved to shift the SRR ESA to resonate at a lower frequency. A planar configuration of Four Stubs Hexagonal Double SRR (FSHD-SRR) ESA metaresonator is proposed to operate sufficiently to cover the WiFi 2.4 GHz band. Then, the proposed design is simulated and fabricated over the entire WiFi 2.4 GHz frequency range from channels 1 (2.412 GHz) to 13 (2.472 GHz) with a reflection coefficient, S11 of less than -10 dB for the extreme channels and -30 dB for the center channel 7 (2.442 GHz).

A study of the intra-body propagation channel between two identical tissue implanted antennas is presented. To investigate the effect of the tissue boundaries, the channel between the two implants is evaluated within a tissue layered numerical phantom with both insulated and un-insulated antenna structures in the MedRadio operating band (2.36-2.40 GHz). The results demonstrate how wave propagation between the antennas inside the same block of tissue is largely unaffected by changes in the peripheral surrounding tissues, irrespective of their material characteristics. On the contrary, propagation across tissue boundaries is affected by the boundary and the path distance within each tissue according to the dielectric parameters involved.

A systematic technique for the accurate implementation of electromagnetic resonance-based wireless power transfer (WPT) implementations by means of diverse metamaterials is presented in this paper. To this aim, two distinct resonating elements are selected, i.e. the edge-coupled split ring resonator (EC-SRR) and the E2 SRR. In particular, the macroscopic properties of these elements are precisely retrieved and the preceding SRRs are then incorporated in the featured WPT scheme. The performance of the system, including the magnetically resonant SRR, is proven to be very promising for distances within a few centimeters, as expected from the initial theoretical analysis, contrary to the case of the electrically resonant elements.

Knowledge of thermal and/or conductivity local changes inside the brain may provide useful information about brain activity. Microwave radiometry may be able to monitor such changes. Based on previous research in brain mapping using microwave radiometry a new prototype near field radiometry system has been used to detect local changes of temperature and conductivity in brain phantom experiments which are herein presented.

This work presents the design, simulations and measurements of a compact 18x12 mm2 monopole antenna fabricated on 1.6 mm-thick FR4 substrate for ultra-wideband (UWB) applications. The antenna exhibits a measured voltage standing wave ratio lower than 2 through the 3.1-10.9 GHz frequency range. The Wireless Baseband Transmission (WBT) scheme has been designed to transmit 1 Gbps digital data streams with Manchester or Polar RZ encodings directly between two monopole antennas placed in an emitter-receiver configuration, at a short distance from each other comprised between 1 and 10 cm. The Bit Error rate (BER) has been measured for different digital pattern lengths.

A zero-index metamaterial unit cell working over a wide frequency band is presented. A three layer superstrate with metamaterial unit cells arranged in a 5 by 5 array is designed and placed over a mircostrip patch antenna with U-slot for antenna gain enhancement. The simulation results show that the gain of the metamaterial antenna is improved by nearly 4 dB throughout the operating band.

The Near-Field Intensity Enhancement (NFIE) of a Distributed Bragg Reflector has been calculated at the presence of a constructive interference at the surface of a Bragg reflector. The Bragg reflector has been constructed using SiO2/GaAs with respective refractive indices of n1=1.5 and n2=3.6. A reflectivity of 0.99986 has been simulated with an electric field enhancement approaching 2. The Bragg reflector is coupled with a Gold dipole nanoantenna to obtain a significant NFIE that is 14 times stronger than that of a Gold dipole nanoantenna above a pure silica (SiO2) surface.

In this paper, based on the inverse transformation optics and Maxwell's equation, a metasurface is designed, which can transformed the incident plane wave into four circularly polarized beams with specific angles. After simplification and approximation, we realize the metasurface by constructing the structure of 3-layered Jerusalem crosses in the three-dimensional structure. The design method has provided novel ideas of the antenna design based on transformation optics.

A new non-reciprocal antenna array has been proposed in this paper for operation in microwave frequencies. The antenna array has been configured using a gyrator with the antenna patch elements through a T-type structure. Implementation of gyrator in the structure, that provides a phase shift of 180 degrees, results in a same beam direction of the forward and backward signals in the proposed antenna array. This proposed novel structure provides high radiation efficiency with beam steering and reduced side lobe levels.

The orbital angular momentum (OAM) beam can be used to significantly increase the communication capacity. In this paper, a reflectarray antenna is proposed and demonstrated for generating arbitrary OAM beams. A new dual-resonance dipole element is employed to implement the conversion between the incident spherical wave and the reflected OAM wave. Besides, this element can provide very good polarization separation and wide phase coverage. Thus, the OAM multiplexing can be achieved in a compact configuration by using independent feeders. As an example, four independent OAM modes, i.e., l=±1 and l=±2, are generated by a Ka-band reflectarray antenna.

In this work, we solve a problem of antenna selection (AS) for a multiple-input multiple-output (MIMO) system under the constraint of the channel capacity maximization is addressed. The biogeography-based optimization (BBO) algorithm is applied on the joint transmitter and receiver AS for the channel capacity function. We apply different BBO migration models for simulated channels. The comparisons with other popular evolutionary algorithms such as the genetic algorithm (GA) and the ant colony optimization (ACO) show the efficiency and the applicability of the BBO algorithm. Results are given for three representative scenarios involving selection of 2x4, 3x5, 4x6 antennas in a 16x16 MIMO system.

Within this paper the use of Wi-Fi in air and in underwater environment using the channels around the 2.4 GHz frequency range that have been standardized worldwide, is presented through simulation and experimental work. Using a bow-tie shaped antenna we study the actual signal strength between underwater and air conditions, while changing the distance between two devices, wirelessly connected with each other.

This paper investigates maximum achievable efficiency of inductive power transfer (IPT) system with arbitrary number of receivers. We derive the formulas of optimal loads and maximum efficiency based on N-port network model. Via analysis and computer simulations, we show that the cross-coupling among receivers does not affect system efficiency if load resistances and reactances are jointly optimized. We also prove that the maximum efficiency is dominated by a so-called system kQ-product, whose square is interestingly, equal to the sum of squares of kQ-products of individual transmitter-receiver links.

In this paper, a novel design of 4×4 microstrip Quasi-Yagi beam-steering antenna array operation at 3.5GHz for future 5G vehicle applications is proposed. This array consists of sixteen element antennas with dimension of 374×374×1.15mm3, which exhibits good bandwidth (impedance bandwidth of single antenna element about 440MHz for S11 less than -10dB at the center frequency of 3.5GHz) and high gain (for single antenna about 7dBi and for antenna array about 5.8~8.76dBi). The beam-steering characteristics in the operation band can nearly achieve omni-directional radiation.

Studies on a massive Multiple-Input Multiple-Output (MIMO) system have been studied in recent years. In a massive MIMO system, antenna elements are arranged not in one dimension but in two dimensions because very large number of antenna elements are used, and the system is called a full-dimension MIMO. In this paper, we generate channel matrices between a transmitter at a base station and user equipments by using a ray tracing technique and evaluate the channel capacity with different places of a transmit antenna array in an indoor environment. In addition, we introduce block SNR maximization and compare the performance with that of block diagonalization. Sum capacity in the case when the BS is placed at the ceiling is larger than one in the case of placing at the wall.

Carrier frequencies beyond 300 GHz have recently received attention primarily due to the potential for impressive capacity for future multi-gigabit communication systems. In this context, this paper compares propagation characteristics of Terahertz links under different weather conditions such as clear sky, fog and rain and then estimates the available bandwidth and the corresponding maximum data rate in the THz band. Results show that values beyond 1Tbps can be achieved under certain conditions for the transmitted power, antenna gains and weather conditions.

A new active steering broadband antenna system solution for automotive is presented in this paper. The system leverages on the available existing MIMO antenna to provide active steering capability to the main antenna whenever the conditions to support MIMO communication are not fulfilled or when the protocol used does not support. The antennas are using dielectric resonator structures and multimode radiator elements in order to support all the most common cellular frequency bands. The active steering capability is achieved by a circuitry controlling the phase and impedance between the main and MIMO antenna whenever they are combined. The simulation results of the prototype are presented and discussed.

Additive manufactured prototypes based on a novel inverted-F antenna design are presented and measured results discussed. Radiation efficiency is computed with the aid of a Wheeler cap box; the resulting ratio of the antenna's quality factor to the lower limit described by Chu is shown to be 1.9 for a spherical variant. Measured and simulated S-parameter results show good agreement, with some evident discrepancies - these are explained by potential unknown changes to the powdered materials during the printing processes, and the rough surface finish of the metallization on the antennas.

This paper presents the folded dipole antenna on the hemispherical PMC shell for the helmet antenna design. The helmet antenna has been required to achieve not only the low-profile and small configuration but also the suppression of the radiation toward a human head. By applying the perfect magnetic conductor boundary to the surface of the hemispherical shell, the suppression of radiation toward the human head and impedance matching can be achieved simultaneously.

The goal of this paper is to show that a reactively loaded antenna is able to provide maximum directivity similar to the one featured by a uniformly excited array featuring the same physical aperture. In particular, it is shown that the superdirectivity behavior of such an antenna can be achieved without compromising the relevant radiation efficiency.

One benefit of electrically small antennas is the reduction in volume occupied by the antenna in a design. In order to further maximize the total volume afforded to the antenna, this paper investigates the impact of two different antenna core compositions that allow for circuit components to be placed within the antenna structure. An electrically small, hemispherical helix antenna realized through a stack of printed circuit boards has been evaluated with two different core configurations: an air core and a composite metal core. The composite metal core consists of both air and copper in order to achieve an integral Faraday cage, which is used to isolate the antenna from the components within the antenna structure.

Bandwidth and Efficiency enhancement by multiport loading of a double notched electrically small antenna is presented in this paper. The technique used is based on the combination of the Network Characteristic Modes (NCM) with an optimization algorithm, in order to find the optimal load values at specified positions. The required loads are found to be simple capacitive loads

This presentation will provide a review of recent examples of in-package antennas operating from X-band to D-band utilizing two different packaging technologies: a) Multilayer organic and b) 3D Printing. The presentation will also discuss pros and cons of each technology,as well as some future directions for the development of low cost, in-package antennas for a variety of wireless applications.

A design of feeding transition for conformal integration of traveling-wave slot antennas in the millimeter-wave regime is presented in this paper. The design utilizes a shielded half-mode substrate-integrated waveguide (HMSIW) bent section to provide an efficient transition from a coaxial connector to the antenna. A curved ground plane, such as the surface of a cylindrical pole, mimics an infinite ground plane and thus minimizes ripples in the azimuth-plane radiation pattern. The design is demonstrated with two antenna applications, including a wideband broad beam antenna and a directive leaky-wave antenna with minimized sidelobe level.

Packaging of terahertz instruments with high-performance antennas is very challenging. Losses of traditional transmission lines such as waveguides, microstrips, and coplanar waveguides go up as the frequency increases. That proves to be a hindrance in integrating commonly used antenna technologies for terahertz instruments. To overcome these shortcoming, researchers have been looking into alternative technologies such as silicon micromachined waveguides and lens based leaky wave antennas which can be integrated without long length of transmission lines. Moreover, availability of new instrument platforms such as CubeSats, SmallSats, and drones have made it necessary to design and develop conformal antennas with low-loss integrated packaging.

There has been some progress in recent years for the development of very low-profile, ultra-light, and high gain antennas that can be integrated on conformal surfaces. Reflectarrays are one such example. However, there are a new class of planar antennas consisting of a textured surface or metasurface (MTS) on a thin support that can provide high gain and efficiency.

This paper describes how low-cost, inkjet-printed, wireless sensors have been developed for real-time monitoring applications. Fully inkjet-printed sensors have been developed to monitor temperature, humidity and gas levels for wireless environmental monitoring. The sensors are integrated and packaged using 3D inkjet printing technology. The package contains an innovative 3D antenna design for orientation insensitive communication. Moreover, in order to demonstrate the benefits of such wireless sensor systems for health care applications, a low-cost, wearable, wireless sensing system has been developed for chronic wound monitoring. The system called 'Smart Bandage' can provide early warnings and long-term data for medical diagnoses. These demonstrations show that inkjet printing can enable the development of low-cost wireless sensors that can be dispersed in the environment or worn on the human body to enable an internet of things (IoT), which can facilitate better and safer living.

Additive manufacturing has been described as a breakthrough of the next industrial revolution, a process with minimal waste and manufacturing time. With new manufacturing techniques, novel new RF structures and sensors can be created with lower costs and minimal time in ways never before possible with previous technologies.