Wireless capsule endoscopy systems utilize a combination of hardware and software devices to ensure the healthcare of a human being. In praise of involved antennas in the overall medical system design, UWB (Ultra-Wideband) range occupies highest ranks in the literature. The low-band of UWB is regarded as the best frequency range, within the approved standards, to realize the better transmission of captured medical images by the capsule inside the SI tract, in terms of high resolution and low-path loss. A variety of passive capsules have been designed and made available in the literature, while the accurate design of the corresponding on-body antenna is lagging. For this purpose, this paper provides an extended study of a recently published on-body antenna operating at 3.75-4.25 GHz band. The measured antenna realizes good directivity of 5.78 dBi and 9.50 dBi towards the body without and with the cavity, respectively. The direction of the proposed on-body antenna beam is targeted to be mounted on the body surface. On-body simulations were run with CST Microwave Studio by involving an abdominal multi-layer model, and followed by navel and back areas of the voxel model to predict the antenna behavior close to different lossy body environments. Later, the antenna structure was measured next to a real human abdomen. Simulation results reveal that the proposed antenna with or without the cavity enables enhanced in-body communication when mounted on the abdomen with less path loss. This is supported by the low power totaling 20 dB at the SI (Small Intestine) tract. Furthermore, on-body measurements confirm the good antenna performance. Consequently, the planar compact antenna is regarded as a good on-body candidate for wireless capsule endoscopy systems.

Estimating polarization information using vector antennas is of great significance in signal processing. However, the antenna patterns are normally assumed ideal without considering practical factors, such as cross polarization. Moreover, pattern calibration is required in data processing. In this work, we first illustrate the polarization estimation method, taking into account the cross polarization of antennas. To simplify the estimation, we introduce a practical co-located antenna pair comprising a sleeve monopole and a windmill loop, which share mostly identical radiation patterns but orthogonal polarizations. The cross polarizations of both antennas are below -20 dB. Besides, the phase and amplitude patterns of both antennas are almost omnidirectional in the azimuth plane, avoiding complicated calibrations. Attributed to orthogonal polarizations, good isolation is achieved, and the envelope correlation coefficient is below 0.01. With the proposed antenna, the axis ratio and phase difference of the incoming wave are reasonably estimated without pattern calibration and compensation. The co-located antenna pair was fabricated, using which the polarization information of a commercial WLAN antenna has been measured.

The aim of this paper is to highlight and elaborate the construction and establishment of a rectangular anechoic chamber (AC) of dimensions 7 m × 4 m × 3 m working from 0.1 GHz to 40 GHz. It is an informative checklist giving an insight on the reckoning of chamber dimensions and selection of appropriate absorbers as per the required specifications. It briefs the key features of validation of an anechoic chamber, namely, shielding effectiveness and reflectivity (quiet zone). It describes the intricacies of the integration of systems such as vector network analyzer (VNA), antenna mounting stands, three-axes motorized antenna rotation control circuitry and customized software. The validation of the established chamber is accomplished for overall shielding effectiveness of -80 dB and reflectivity of -40 dB in one cubic meter area at the receiving antenna or antenna under test (AUT) region far away from transmitter say, at 5.5 m separation. This paper covers the measurement results of three broadband horn antennas which can be used as reference antennas for characterization of other antennas in the chosen frequency range. The entire report will certainly be a guideline for any reader or aspirant who is interested in the development of a similar anechoic chamber and looking for complete intricacies.

This paper presents the design of a compact size, passive, W to K band subharmonic mixer with post-wall waveguide (substrate integrated waveguide) RF input interface. The mixer is based on a silica-glass structure where the post-wall waveguide and microstrip line are on separate substrates. This configuration maximizes the performance as the substrate thicknesses can be separately optimized for the lowest loss and mono-mode operation. Integration of different types of guiding structures also allows realization of e.g. millimetre-wave waveguide filters and microstrip circuits in a single structure, while preserving low-cost, low-weight and compact size. Furthermore, post-wall waveguides can be easily interfaced with conventional rectangular waveguides, as demonstrated in the paper, which simplifies millimeter-wave circuit packaging and eventual system integration. Design methodology of the mixer and transition circuits as well as measurements are presented. Minimum conversion loss of 19.6 dB was achieved at 86 GHz with 13.7 dBm/32.4 GHz LO signal. The presented design would be suitable for the future W-band cellular, radar or satellite communication systems.

The electromagnetic circumstance of the small-room of substation turns to be more complex with the increase of the voltage level of the power grid. In this paper, a physical model for protective small-room of substation on the basis of the random plane wave hypothesis and wave-chaotic approach is constructed to get the scattering parameters, combining the Random Coupling Model (RCM) to deduce inducted voltage of coaxial cable terminal and making statistical analysis and prediction for electromagnetic quantity coupled to the cable terminal. The results of simulation by FEKO show the validity of the method introduced in this paper, which provides a guidance for the electromagnetic protection in the protective small-room.

Beam-steering antennas especially with Butler matrix feed network are an effective remedy for wireless communications systems troubles such as disruptive effects in mm-wave frequency. In this work, a novel 4×4 Butler matrix feed beam steering antenna is designed at 35 GHz. A zeroth order resonance antenna element is used for bandwidth and radiation efficiency increment. To increase the gain of the antenna a novel mm-wave Fabry Perot layer which is composed of a partially reflective surface is designed. All designing steps are presented.

In this study, a new multiple-input-multiple-output (MIMO) antenna array is introduced for fifth-generation (5G) smartphones. Its schematic contains eight planar inverted-F antenna (PIFA) elements placed at edges of the mobile-phone mainboard with a 75×150×0.8 mm³ FR-4 substrate. The ground plane and antenna resonators are etched on the back layer of the mainboard. By employing arrow strips between the adjacent elements, the frequency bandwidth and isolation level of the PIFA radiators are improved. The proposed smartphone antenna array is designed to support the spectrum of commercial sub 6 GHz 5G communication and cover the frequency range of 3.25-3.85 GHz with isolation levels better than -15 dB. Due to compact size and corner placements of the PIFAs, the presented MIMO antenna array occupies a small part of the board. In addition, the proposed smartphone antenna array provides not only sufficing radiation coverage supporting different sides of the mainboard but also the polarization diversity. The MIMO performance and characteristics of the proposed smartphone antenna design in the presence of the user phantom are also discussed.

To make a truly compact size system on-chip (SoC) device for wireless bio-telemetry application, the design of a miniaturized on-chip antenna (OCA) with enhanced gain becomes a prime challenge in recent time. Unsuitable Si (Silicon) substrate and relatively larger antenna size at lower microwave frequencies make it even more challenging for the researchers. In this work, an OCA is designed on a low resistive (ρ = 10 ohm.cm) Si substrate by using standard CMOS technology process. The top metal layer of CMOS layout has been used for designing the antenna to reduce fabrication complexity. By using slot miniaturization technique, the proposed antenna size of λ₀/22 x λ₀/21.4 mm² is achieved and operable at ISM 915 MHz band for biotelemetry applications. A gain enhancement technique for OCA is proposed by introducing a 0.2 μm thin film of Cobalt Zirconium Oxide (CoZrO) ferrite material, and the gain is enhanced by +12.28 dB with the bandwidth and fractional bandwidth (FBW) of 1.14 GHz and 124%, respectively. The simulation results of the proposed antenna with coating of bio-compatible material show its potential applicability for implantable bio-telemetry applications. An equivalent circuit of the proposed OCA is presented and verified by ADS circuit simulator.

In this paper, we present the design and fabrication of a novel class of emerging waveguide filters based on chained-functions at the millimeter-wave band. The derivation of chained-functions by chaining of prescribed generalized Chebyshev seed functions based on the partition theory is presented in details, and the implementation to waveguide technology is proposed and evaluated. The waveguide filter is fabricated through two different technologies, namely the Computer Numerical Control (CNC) milling technology and the Direct Metal Laser Sintering (DMLS) based additive manufacturing technology. The chained-function filters, which lie in between the Butterworth and Chebyshev filters, inherit the salient properties of both Butterworth and Chebyshev filters. Therefore, the chained-function waveguide filter exhibits filtering responses that have a superior rejection property and a lower loss with reduced sensitivity to fabrication tolerance than the standard Chebyshev waveguide filter. The efficiency of the proposed waveguide filter is confirmed both theoretically and empirically, using the CNC and DMLS processes. The issues of a higher manufacturing tolerance and apparent surface roughness associated with the DMLS method are found to be electrically insignificant when the chained-function concept is adopted in waveguide filter design. In general, the measured results of all the realized waveguide filters agree well to those of the simulation models. These results positively demonstrate that the chained-function concept has robust properties for rapid, high-performance, low-cost, and sustainable filter design and implementation, particularly for higher millimeter-wave frequency bands and for narrow-band applications.

In this work, a Tri-Band frequency reconfigurable antenna for LTE (Long Term Evolution)/WiFi (Wireless Fidelity)/ITS (Intelligent Transportation Systems) applications is presented. The proposed design consists of a wine glass shaped slotted radiating patch along with a switchable rectangular ring type slot on the ground plane. This structure operates in three different states viz. state-1, state-2, and state-3 at 4.5 GHz (LTE band), 5.9 GHz (ITS band), and 3.8 GHz (LTE band)/5 GHz (Wi-Fi band), respectively, with an overall compact size of 30 × 30 × 0.762 mm³. Multi-band resonances are obtained by incorporating slots in the main radiating element and ground plane. Moreover, switching among these bands is achieved by placing two PIN diodes at optimized positions on the rectangular ring slot in the ground plane. For the proposed design, good agreement between simulated and measured results is obtained in all the three operating states of the design, which makes it suitable for compact reconfigurable systems.

Accomplishing high efficiency with acceptable output load power is a formidable design challenge in resonant wireless power transfer (WPT) system employed for charging Electric Vehicle (EV). This necessitates a trade-off among the assorted parameters like coil quality factor, coupling coefficient and electric load for performance enrichment of resonant WPT system. It is realized that the high value of quality factor does not ensure higher power transfer efficiency but it is largely influenced by the electric load. For each coupling coefficient there exists an optimum load for which maximum power can be delivered. It is also perceived that for a fixed vertical separation gap of the coils, increasing receiver coil quality factor has no profound effect on the output load power as well as efficiency. The circuit model based analytical results agree well with the comprehensive experimental results and elucidate the strategic design guidelines for a competent wireless electric vehicle charging system.

Modeling wave propagation often requires a truncation of the computational domain to a smaller subdomain to keep computational cost reasonable. The mere volume of papers on absorbing boundary conditions indicates that a perfect solution is not available. A method is proposed that is exact, at least in the case of a time-domain finite-difference scheme for the scalar wave equation. The word `exact' is used in the sense that there is no difference between a computation on the truncated domain with this method and one on an enlarged domain with reflecting boundaries that are placed so far away that their reflections cannot reach the original domain within the modeled time span. Numerical tests in 1D produce stable results with central difference schemes from order 2 to 24 for the spatial discretization. The difference with a reference solution computed on an enlarged domain with the boundary moved sufficiently far away only contains accumulated numerical round-off errors. Generalization to more than one space dimension is feasible if there is a single non-reflecting boundary on one side of a rectangular domain or two non-reflecting boundaries at opposing sides, but not for a corner connecting non-reflecting boundaries. The reason is that the method involves recursion based on translation invariance in the direction perpendicular to the boundary, which does not hold in the last case. This limits the applicability of the method to, for instance, modeling waveguides.

We analyzed the effect of loss and coupling to EIT metamaterials using circuit approach, giving the effect of two parameters: coupling and loss on the resonant property of the EIT metamaterials. To verify the results of the circuit analysis, simulations and experiments were performed. The structures were fabricated with superconducting NbN and varied temperature to verify the effect of loss. The distances were adjusted to observe the effect of the coupling strength. The results of simulations and experiments were consistent with the circuit analysis.

This paper is presented to provide an overview on frequency selective surfaces and techniques to achieve tune-ability in frequency selective surface (FSS). FSS array element with specific arrangement on the dielectric surface either transmits (pass-band) or reflects (stop-band) partially or completely with resonance of the structure in tune with the frequency of electromagnetic wave. Tuning devices like PIN or Varactor incorporated in the structure tune the performance. The recent researches on FSS structures classifying them into structural classification and mechanisms to change the operating resonance frequency dynamically by changing the bias of the tuning devices like PIN or Varactor diode have been studied and detailed in this review article. Tune-ability allows the FSS layer filter to adapt to spectral changes and to compensate for the best performance in terms of bandwidth, gain, and directivity. We also focused important performance parameters, particularly on how development in this field could facilitate invention in advanced electromagnetics.

In this paper, a design of a low profile cavity backed antenna consisting of bilateral slots is developed for generating two frequencies. Here, the whole antenna including substrate integrated waveguide (SIW) cavity is constructed from only one substrate with the height of 0.026λ₀. The long transversal slot at the ground plane is excited by TE₂₁₀ mode of the cavity and produces one hybrid mode resonance at 9.85 GHz. When the short transversal slot cut is incorporated in the top portion of the cavity, TE₃₁₀ mode is perturbed, which results in generating an additional hybrid mode resonance at 14 GHz. Both these hybrid modes help to create a dual-band response. A sample of the proposed design is fabricated, and it has been verified experimentally that the bandwidths of the proposed design are 530 MHz (5.48%) and 440 MHz (3.15%) at lower and higher resonant frequencies, respectively. The antenna renders measured peak gains of 6.62 dBi and 6.44 dBi at 9.85 GHz and 14 GHz, respectively. The cross-polarization level of maximum -20 dB and same polarization planes are obtained at both the operating frequencies.

Millimeter wave (mm-Wave) is today's breakthrough frontier for emerging wireless mobile cellular networks, wireless local area networks, personal area networks, and vehicular communications. In the near future, mm-Wave products, systems, theories, and devices will come together to deliver mobile data rates thousands of times faster than today's existing cellular and Wi Fi networks for an example from the era of 3G, 4G towards 5G mobile communication in near future. This paper presents studies on rain attenuation at 6 GHz and 28 GHz, which is widely used for local multipoint distribution service deployment by using the measured and prediction methods for terrestrial microwave links point to point in tropical regions. Besides this, discussion and comparison of five different reduction factor models have been presented. Several models have been proposed by researchers to account for the horizontal variation of rain fall. Five rain attenuation prediction models at tropical region are analyzed. The models are ITU-R model, revised Moupfouma model, revised Silva Mello model, Abdul Rahman model, and Lin model which have been analyzed. The objective of these studies to identify rain attenuation using prediction model for 5G network in tropical region for country like Malaysia. This study been carried out with setting of an experimental test bed. A link of path length 0.2 km was set up in Johor Bahru, Malaysia. Both the transmitter and receiver operate at frequencies of 6 GHz and 28 GHz. A tipping bucket rain rate used, and all the data have been recorded using data logger. At the end of the analysis, it is found that all the five models predict rain attenuation at less than 1 dB and 11 dB for operating microwave frequency at 6 GHz and 28 GHz for 5G Network, This findings will be useful for future 5G network designers to consider the effect of rain impairments especially in tropical region.

A two port multi-input-multi-output (MIMO) dielectric resonator (DR) antenna (DRA) is proposed with circularly polarized radiation. The antenna geometry allows to find circular polarization and improved impedance bandwidth by reducing the separation between the DR elements. The isolation between the ports of the antenna remains more than 15 dB in the operating passband even after reducing the separation between the radiating elements. The antenna provides the 10-dB impedance and 3-dB axial ratio bandwidth of 34.85% and 4.55%, respectively. The MIMO performance of the proposed antenna is confirmed by calculating the parameters like envelop correlation coefficient, diversity gain, mean effective gain, channel capacity loss, and the total active reflection coefficient. The proposed antenna can be utilized for C-band applications.

This paper discusses a circular loop frequency selective surface (FSS) using a 3-D (three dimensional) printed technique. The proposed FSS design consists of a metallic patch having a circular loop printed on one side of Acrylonitrile Butadiene Styrene (ABS) material. This design is used for harmonic radar applications at 5 GHz resonant frequency. Various FSS parameters are discussed to show the effect on the resonant frequency. To make fabrication process easier and cost-effective, transmitting and receiving antennas are also printed using a 3-D printing material. 3-D printing offers cost-effective fabrication technique compared with other conventional techniques and helps in rapid prototyping. The fabricated prototype is validated with the experimental results that show good agreement between simulated results and the measured ones.

We provide a conceptual and theoretical analysis of nonsinusoidal antennas with emphasis on how electromagnetics and communication theories can be integrated to propose ideas for near-field (NF) communications systems utilizing future antennas. It is shown through rigorous analysis that in nonsinusoidal antennas it is possible to derive and solve ordinary differential equations giving specialized time-domain excitation signals that lead to exact cancellation of the near field at specific radiation spheres. This opens the door to building NF communications systems with far-field-like communication receiver infrastructures utilized if the receive antenna is placed at the special sphere where the NF component is made to vanish. We deploy exact current Green's function analysis method and completely avoid the use of any frequency-domain method. Complete expressions of the electromagnetic near- and far-field contributions to all signals propagating from the source to the receiver are then derived and their physical content discussed. The distortion effects and signal-to-noise rations due to the near-field are also identified and derived theoretically. It is found that using this specialized pulse excitation method in nonsinusoidal antennas, distortion caused by near-field components can be eliminated at critical distances between the source and the receiver. Realization issues of this system are briefly discussed together with some potential applications.

A rectangular Dielectric Resonator Antenna (DRA) four element Multiple in Multiple Out (MIMO) is proposed for 5G application, and each element is supplied with slot-coupled microstrip feed. The entire construction has a dimension of 20 mm × 40 mm. Four Dielectric Resonators are mounted exactly above the slot. In order to improve the isolation, metamaterial is printed on top of the dielectric resonators, which move away the solidest coupling fields. As the metamaterial structure interacts with the electromagnetic fields, field distributions are disturbed which results in reduction of coupled fields. Since the metamaterials are printed on top of the dielectric resonator, the proposed antenna structure has simplest and compact design. The proposed structure is operating with an impedance bandwidth of 2.23 GHz with operating range from 26.71 GHz to 28.91 GHz, which covers the 28 GHz (27.5 GHz-28.35 GHz) band allotted by Federal Communications Commission (FCC) for 5G application. With all four-port excitation, the proposed structure shows a broadside radiation pattern with gain above 7 dBi in the entire operating bands. The Envelope Correlation Coefficient (ECC) for operating bands is within the target value. They are designed and fabricated to validate the proposed antenna. The simulated and measured values are nearly equal, which means that the proposed MIMO DRA is the right choice for mm-Wave 5G implementation.