In this work, the design of a high sensitivity hydrostatic pressure sensor based on one-dimensional photonic crystal (1DPC) containing polymeric materials has been proposed and investigated, theoretically. The proposed structure consists of alternate layers of polystyrene (PS) and polymethyl metahacrylate (PMMA) with a defect of layer of PS, PMMA and air, respectively, in the middle of the PC structure. The sensing principle is based on the shift in the peak of transmitted wavelength when the hydrostatic pressure is applied on 1DPC. In order to obtain the transmission spectrum of 1DPC structure transfer matrix method (TMM) has been used. From the analysis it is found that with the increase in hydrostatic pressure transmission (or resonance) peak shifts towards the lower wavelength side with respect to the center wavelength. The average sensitivity (Δλ/ΔP) of the proposed sensor is found about 0.948 (nm/MPa) with polymer defect and 0.92 (nm/MPa) with air defect in the mid-IR frequency region, and the applied pressure range is 0 to 200 MPa.

The variation in flight attitude, line-of-sight, and speed of unmanned aerial vehicles (UAVs) affect their polarization-dependent coupling cross-section and resultant compatibility to pulsed electromagnetic energy. Here, we present the out-of-band electromagnetic compatibility (EMC) effects of UAV frame material and shape on the UAV subcomponents. Characteristic mode analysis (CMA) is employed to study the fundamental modes supported by UAVs which facilitate the interpretation of its electromagnetic response and the prediction of its effect on the nearby components. Using CMA, we develop a framework that optimizes the placement of wires and traces of printed circuit boards (PCBs) on the frame mitigating interference from undesired electromagnetic sources. A 3-D scanner is used to provide four versions of a quadrotor UAV to study the frame shape effect on the coupling. Materials of differing permittivity are assigned to these frame versions to assist in understanding the material effect on the EM coupling to the UAV.

With the supersonic growth of mobile data demand, the fifth generation (5G) mobile network would exploit the extensive amount of spectrum in the millimeter-wave (mm-Wave) bands to tremendously increase communication capacity. There are conceptual differences between mm-Wave communications and other existing communication systems, in terms of high propagation loss, directivity, and sensitivity to blockage. These characteristics of mm-Wave communications present several challenges to completely exploit the potential of mm-Wave communications, including integrated circuits and system design, interference management, spatial reuse, anti-blockage, and dynamics control. 5G mobile communication systems with sub-6 GHz and millimeter-wave bands are already replacing 4G and 4.5G systems as an evolution towards higher-speed mobile communication and wider bandwidth. From the hardware perspective, the 5G-band causes the miniaturization of RF components including the antennas. In this article, an overview of recent research is presented that discusses design challenges and measurement considerations for various types of compact 5G antennas.

We present a low-cost and high-performance 5-bit programmable phased array antenna at Ku-band, which consists of 1-bit reconfigurable radiation structures, digital phase shifters, and coplanar waveguide feeding network. The 1-bit reconfigurable radiation structure utilizes symmetric geometries and PIN diodes to form stable 180° phase difference. The digital phase shifter provides 168.75° phase difference and together with the radiation structure form a 348.75° phase coverage. The antenna operates between 14.4 and 15.4 GHz, and the overall array contains 24×2 elements with each of them being individually addressable. By changing the states of the diodes and thus adjusting the phase coding sequences of the array, the antenna achieves 0°-60° precise beam scanning at 14.8 GHz, with the sidelobe level, cross-polarization, and gain fluctuation being less than -16 dB, -26 dB, and 2.4 dB, respectively. A prototype was fabricated to verify the design, and the measurement results agree well with simulations. Compared with traditional phased arrays composed of numerous phase shifters and T/R components, the proposed antenna features high performance, high flexibility, low profile, and low cost. The antenna provides a new and feasible solution of wavefront steering and will benefit the various application scenarios.

In this paper, dual-band split ring monopole antenna structures for 5G sub-6 GHz and WLAN applications are proposed. The antenna structures are designed from a rectangular annular ring monopole antenna. A compact dual rectangular split ring monopole antenna is designed to operate over dual bands. The two split rings are connected through a common arm. The structure is optimized to provide S₁₁ ≤ -10 dB over 3.3-3.6 GHz and 5.15-5.5 GHz for 5G and WLAN applications. In the second dual-band antenna, a slot is cut in one of the arms to form another closed rectangular ring to further reduce the dimensions of the antenna. This structure provides S₁₁ ≤ -10 dB over 3.3-3.6 and 5.5-5.9 GHz for 5G, WLAN and V2X applications. The two bands can be easily controlled as the dimensions of two rings determine the resonant frequencies of the two bands, and one of the arms of a ring is unresponsive to lower band and affects upper band only. Both antennas offer nearly omnidirectional radiation patterns in both bands. The two prototype antennas are fabricated on a 0.17λ₀×0.19λ₀ and 0.15λ₀×0.19λ₀ FR4 substrate, where λ₀ is the free-space wavelength corresponding to 3.3 GHz. The measured results agree with the simulated ones.

A new unterminating method for coaxial to waveguide transitions is presented. The coaxial to waveguide transitions are modelled and the ABCD matrices of the transitions are obtained. The measured scattering parameters for the thru and short-circuit calibration standards match well the simulated scattering parameters computed from the ABCD matrices. To complete the validation of the proposed unterminating method, this method is applied to the measurement of complex relative permittivity for three different dielectric materials, by using the Nicolson-Ross-Weir (NRW) transmission/reflection method. The dielectric samples are inserted one by one into a waveguide section, which is connected between two coaxial to waveguide transitions. The two transitions are de-embedded from the measured scattering parameters of the embedded waveguide section, by using the method proposed in this paper. The values obtained for the complex relative permittivity are in good agreement with those reported by other authors, for all three dielectric materials. The results presented in this paper were obtained for a frequency band ranging from 25 to 40 GHz.

The study of the thermal effect caused by exposure to electromagnetic fields is a focus of this research. To quantify the induced current and temperature distribution in the human body an assessment tool for the frequency range of 50 Hz to 110 MHz has been developed. The major contribution consists of providing a quantitatively accurate and relatively simple model. The formulation of the problem is based on a simplified cylindrical representation defined by the anatomical parameters of the human body. The bio-thermal modeling is carried out in two stages. Firstly, the electromagnetic analysis is based on the transmission lines (TL) theory. Secondly, a thermal modeling based on the thermal networks model (nodal method) is approached. This allows us to quantify the corresponding thermal gradients in the human body.

A wideband compact shark-fin antenna operating in a frequency band from 2.86 GHz to 7.68 GHz is presented. The proposed design is realized on a substrate material of ``Rogers 4003C'' with ε_r = 3.48, tanδ = 0.0027, and substrate thickness 0.81 mm. The antenna is designed to operate at a center frequency of 5 GHz with an operating bandwidth of 4.82 GHz (96.4%). The bandwidth covers the lower band and mid band of 5G at resonant frequencies of 3.5 GHz and 5.8 GHz, respectively. The realized gain of the proposed antenna is 4.1 dBi and 5.35 dBi in the lower band and mid band, respectively. The proposed antenna is designed and simulated. It is also fabricated using photolithography techniques and measured using an R&S vector network analyzer. Good agreement is obtained between the simulated and measured results.

In this paper, a standard ray tracing model based on Geometrical Optics (GO) is proposed for predicting the signal strength of Wireless Sensor Network (WSN), ZigBee nodes, in an indoor environment. The signal strength is calculated analytically. The results are compared with numerical analysis implemented in FEKO computational electromagnetic software, and agreement is demonstrated. Also, the model is verified by a simple measurement campaign in a straight corridor section of commercial building, and results agreement is obtained. The results show that the proposed technique is capable of predicting the signal strength of WSN sensors in a corridor section of indoor environment with good accuracy, fast calculation time, and low computational resources and complexity. The proposed analytical model and measurement dataset can help WSN designers select the best locations of ZigBee nodes in a straight corridor section with good signal quality.

The electromagnetic wave perfect absorption of metamaterial is focused on by scientists currently. Conventional studies typically use a basic unit cell and then develop the entire structure in production. In this paper, we study and use a full-sized twisted metamaterial structure with the expectation that this structure will reveal outstanding advantages and possess excellent electromagnetic absorption properties. The structure of the twisted metamaterial consists of two coincident layers of cyclic lattice stacked on top of each other. When one lattice layer rotates at a specified angle relative to the other, it generates a new lattice configuration and increases the absorption of the structure. Therefore, the frequency band widens up to 6 GHz.

Raindrop sizes were measured in Douala, Cameroon (4˚03N, 9˚42'E) using a Parsivel disdrometer. The data obtained are used for the analysis of the drop size distribution (DSD) and specific rain attenuation modeling in the 5-150 GHz frequency range. The Lognormal and gamma distribution models are employed using the method of moments estimation, considering the third, fourth, and sixth-order moments. The parameter fits for the two DSD models proposed here for different values of rain rates are investigated. The specific rainfall attenuation using the Douala DSD models is compared to the ITU-R models in vertical and horizontal polarisation and models for some countries with different climates such as semi-arid, tropical, and subtropical ones in Africa. The comparison with the ITU-R model shows significant differences occurring at high frequency with both high and low rainfall rates. The comparison with other regions of Africa also shows that Douala is characterized by equatorial climate, and Durban characterized by subtropical climate shows similar rainfall attenuation characteristics at operating frequency range 10 ≤ f ≤ 150 GHz, especially at a lower rain rate. At a higher rain rate, specific rain attenuation at Douala is always higher than in other African locations. The proposed models are very important for the determination of rainfall attenuation for terrestrial and satellite systems.

In this paper, a novel wideband gyrator based on a ferrite coupled line design approach and realized in coplanar waveguide configuration is presented. The ferrite coupled lines are proved to demonstrate typical unique properties. The design of the optimum coupled lines has shown an almost 1 dB/3 dB insertion loss for even/odd modes excitation, respectively. Also, for single excitation, the power is divided at output ports with insertion loss almost equal to 3 dB and 5 dB, good matching and isolation between output ports (less than -15 dB). The bandwidth of the designed coupler is proved over the bandwidth of 7 GHz-11 GHz. As an application, a novel gyrator is introduced and covers the same coupler bandwidth. The performance of the gyrator is optimized using full-wave simulations.

In this paper, a compact and highly sensitive refractive index plasmonic sensor, based on a metal-insulator-metal (MIM) waveguide coupled to double hexagonal ring-shaped resonators in the mid-infrared range, is proposed and analyzed using the finite-difference time-domain (FDTD) method embedded in the commercial simulator R-soft, where it has been found that the transmission peaks and dipspositions can be easily manipulated, by simply adjusting the structural parameters of the proposed design, such as the inner side length and the distance between the centers of the two hexagonal ring resonators. So, these parameters have a key role in the sensor's performances, and it is clearly noticed from the results, where a linear link between the refractive index of the material under testing and its wavelength resonances was established. Furthermore, the maximum achievable linear sensitivity was S = 4074 nm/RIU, with a matching sensing resolution of 2.45 x 10^-6 RIU; the temperature sensitivity is around 1.55 nm/°C; and the highest linear sensitivity is S = 3910 nm/RIU in 0-200 g/L glucose concentration, making this proposed sensor an attractive one, to be implemented in high-performance nano and bio-sensing devices.

Doppler Ultrasound as the gold standard for noninvasive arterial pulsation monitoring has limitations such as dependency on the operator and absence of acoustic window in some patients. Recently, mm-wave has been propounded as an alternative modality for biomedical diagnostics. However, heartbeat monitoring using mm-wave modality has been experimentally investigated only for external carotid artery, and its usage for deeper arteries has not been proved, yet. This study investigates the feasibility of mm-waves in the monitoring of non-superficial arteries. A continuous-wave (CW) reflectometer sensor is used for sensing pulsations exploiting the Doppler effect. The artery mimicking tube passes through an artificial agar-oil skin phantom. A peristaltic pump circulates the liquid through a tube. An antenna is placed in direct contact with the phantom without any coupling liquid. First, we investigate the optimum frequency of the given antenna in its impedance bandwidth [16 GHz-20 GHz]. Using the optimum frequency, the pulsation of an ar-tery with a 1.6 mm diameter, placed in the depth of 16 mm, and has less than 0.02 mm radial oscillation amplitude was easily detectable.

A hexagonal cavity backed antenna based on HMSIW is proposed to operate at 5.2 GHz and 5.8 GHz frequencies. The TM₀₁₀ and TM₁₁₀ modes of the hexagonal cavity resonator have been chosen to excite the structure. Afterwards, an HMSIW hexagonal cavity is formed by splitting conventional hexagonal cavity resonator along a magnetic wall. This enables a 50% reduction in size without affecting the antenna operating frequency. A rectangular slot is etched at the centre of the magnetic wall to curtail TM₁₁₀ mode operating frequency. The dimensions of the slot are optimized to adapt TM₁₁₀ resonant frequency to the desired frequency. In free space, the resulting antenna accomplished a peak gain of 5.5 dB and 4.3 dB at centre frequencies of 5.2 GHz and 5.8 GHz respectively. In the vicinity of pork tissues, the antenna exhibits a peak gain of 4 dB at 5.8 GHz along with an efficiency of 87.2%.

A study is presented of several types of nondiffracting and slowly diffracting spatiotemporally localized waves supported by a simple dielectric medium moving uniformly with speed smaller or larger than the phase speed of light in the rest frame of the medium. The Minkowski material relations are not independent in the case that the speed of motion equals the phase speed of the medium; hence, the electric displacement and magnetic induction vectors cannot be uniquely determined from them. Following, however, a waveguide-theoretic approach, separate equations can be written for the longitudinal and transverse (with respect to the direction of motion) electromagnetic field intensities. The fundamental solutions associated with these equations provide a uniform transition between the cases of ordinary and Čerenkov-Vavilov radiation. The equation satisfied by the longitudinal field components in the absence of sources is examined in detail. In the temporal frequency domain one has an exact parabolic equation which supports accelerating beam solutions. The space-time equation supports several types of nondiffracting and slowly diffracting spatiotemporally localized waves. Comparisons are also made with the acoustic pressure equation in the presence of a uniform flow.

In this paper, the optimized results of multi-beam forming for an active phased array antenna are presented. In the case of a horn radiator, to implement equal main beamwidths and a low side-lobe level in the principal planes, a circularly polarized dual-mode horn antennawith the gain over 14.5 dBi is designed and fabricated at the Ka-band, which is composed of a conical horn, polarizer, and transducer. In the case of multi-beam forming, when several main beams are simultaneously generated within a limited scanning range, large side-lobes can be observed among the main beams. To overcome this phenomenon, an evolutionary technique, such as a genetic algorithm is applied to the optimization of a multi-beam pattern. It is shown that the proposed method can significantly reduce the outer side-lobe level as well as the inner side-lobe level of the simultaneous multi-beam pattern.

Compared to crystalline silicon solar cells, thin-film solar cells are inexpensive, but a weak absorption of sunlight at a longer wavelength is a significant issue. In this perspective, an efficient light trapping mechanism is needed to facilitate the light-guiding in enhancing light absorption. This paper presents a theoretical investigation of ultrathin amorphous silicon (a-Si) solar cells using the rigorous coupled-wave analysis (RCWA) method. We noticed broadband light absorption of the designed solar cell due to an efficient light trapping geometry. Our proposed design is composed of anti-reflection coating (ITO), an absorbing layer (a-Si), a back reflector (Ag-substrate), top-indium tin oxide (ITO), and bottom-silver (Ag) nanogratings. Using an Ag-back reflector with diffraction gratings demonstrated the improved diffraction and scattering of light, which enhanced light absorption within a 50 nm thick absorbing layer. Compared to the reference solar cell, the proposed ultrathin solar cell endorsed the enhanced photovoltaic conversion, i.e., 19% and 23%, corresponding to the transverse electric (TE) and magnetic (TM) polarization conditions. Furthermore, we explore the investigations of light absorption, current density, field distributions, reflection, transmission, and parasitic losses for the optimal design of ultrathin film (a-Si) solar cells.

Generalized Lorentz-Mie Theory (GLMT) provides analytical far-field solutions to electromagnetic (EM) scattering of an aggregate of spheres in a fixed orientation. One of the computational codes that implements the GLMT calculation is that provided by Xu, dubbed GMM which returns EM responses such as the extinction cross section, σ_ext, given the information of incident wavelength, particle arrangement, the common radius, and reflective indices of the aggregate. We have attempted to represent the GMM code in the form a neural network dubbed NNGMM. The NNGMM obtained was stress tested and systematically quantified for its accuracy by comparing the σ_ext predicted against that produced by the original GMM code. The σ_ext produced by the NNGMM for arbitrary aggregates at random wavelength yielded a good fidelity with respect to that calculated by the GMM calculator up to an R-squared value of above 99% level and mean squared error of ≈5.0. The realization of NNGMM proves the feasibility of representing the GMM code by a neural network. The optimally-performing NNGMM obtained in this work can serve as an alternative computational tool for calculating σ_ext in place of the original GMM code at a much cheaper cost, albeit with a slight penalty in terms of absolute accuracy.

In this article, we focus on metric space in Finsler geometry and propose a method of ship detection in synthetic aperture radar (SAR) amplitude image based on Finsler information geometry. This provides deep unified perspectives of Finsler geometric application. The proposed method consists of three stages: The Weibull manifold model is used to represent the statistical information of intensity SAR images; then the Finsler metric is constructed to realize the distance measurement between probability distributions in Weibull manifold space; finally, Finsler metric space is used to achieve saliency representation and detection of ships. Theoretical analysis and comprehensive experimental results demonstrate the robustness and effectiveness of the proposed approach using typical real SAR images.