This paper introduces a novel design of an embedded stacked Rectangular Dielectric Resonator Antenna (RDRA). The antenna structure incorporates two distinct materials, namely PLA (Polylactic Acid) and Alumina, possessing dielectric constants of 3.45 and 9.9, respectively. A coaxial probe is employed to feed the antenna, enabling efficient signal transmission. The simulated results indicate the presence of two distinct resonance frequencies, which are 9.4 GHz and 10.6 GHz. Furthermore, the simulated antenna exhibits a maximum gain of 7.7 dB at 10.6 GHz, while demonstrating a wideband characteristic spanning approximately 22.7% of the frequency band between 8.75 GHz and 11 GHz on the measurement. The design and simulation of the RDRA are carried out using CST 2020 microwave studio, ensuring accurate and reliable results. The proposed antenna configuration is well suited for X-band applications such as radar and satellite systems.

Phase holographic metasurfaces encode the phase profiles of holograms in metasurfaces formed by the meta-atom arrays, and accurately modulate the field distribution in desired region. Iterative optimization methods or data-driven learning methods are used to retrieve the phase profile under the given physical setups, such as working wavelength λ, metasurfaces' period ∆x, and image distance Z. However, those methods usually repeat the optimization or training process to retrieve the phase profile for different physical setups. Here, we propose a generalized phase retrieval model (GPRM) based on physics-inspired network to retrieve the phase profile from the input λ, ∆x, Z, and desired image without retraining the neural network. The GPRM consists of deep neural network (DNN), parabolic phase, and Fresnel diffraction propagation, which is able to generate phase profile with high reconstruction quality in extraordinary broadband, such as visible, terahertz, and microwave region. By combining with corresponding meta-atom pool, the proposed method has great potential to design versatile meta-devices for image display, data encoding, and beam shaping. Furthermore, the proposed method accelerates the design of Fresnel phase hologram, which can cooperate with programmable metasurfaces to realize dynamic three-dimensional or full-color display.

The paper focuses on the design, measurement, and performance analysis of a high-gain cross-orthogonal series fed two dipole antenna (STDA) arrays with side-wall reflectors. The antenna is specifically designed for 4G Long Term Evolution (LTE) and sub-6 GHz 5G band applications. The designed antenna is capable of operating at multiple frequencies aiming to support 4G LTE and the sub-6 GHz 5G application bands. To improve the radiation characteristics and prevent coupling effects in the presence of side-wall reflectors, parasitic strip pair directors are included in the antenna design. Furthermore, the performance of the designed STDA is evaluated by forming different array configurations, such as 2×1, 2×2, and 2×3 arrays. The various array configurations are proposed to investigate the effect of the projected array arrangements on the radiation pattern, impedance bandwidth, and gain characteristics. The results of the measurements show that the radiation characteristics of the antenna has improved significantly. The proposed antenna operates at six distinct frequencies for S₁₁≤-10 dB. The operating frequencies at 1.8, 2.35, and 2.6 GHz can be utilized for LTE and 3.2, 4.2, and 5.2 GHz can support sub-6 GHz 5G bands. The antenna is characterized by its compact size, measuring around 89 mm × 71 mm, while still achieving high gain of 12.3 dB for single STDA element with parasites and with reflector. These results emphasize the importance of the proposed design, which incorporates parasitic strip pair directors and side-wall reflectors. This design methodology plays a crucial role in enhancing the performance of the prescribed STDA array for both 4G LTE and sub-6 GHz 5G applications.

Conventional solid-state plasma devices encounter limitations in terms of the concentration and distribution uniformity of solid-state plasma, which adversely affects their microwave characteristics and overall antenna system performance. In this study, we propose a novel heterogeneous SPIN diode with multi-region compensation effects aimed at addressing this challenge. By incorporating SiGe regions within the intrinsic region of the device, we enhance the carrier injection ratio, effectively compensating for the rapid attenuation of solid-state plasma. As a result, a high-concentration and uniformly distributed solid-state plasma region is achieved within the SPIN diode, surpassing a concentration threshold of 1×10¹⁸ cm^-3 within the intrinsic region. Through extensive simulations utilizing Sentaurus TCAD software, we demonstrate notable improvements in plasma concentration, distribution uniformity, and other key electrical parameters compared to traditional devices. The presented findings mark significant advancements in the realm of silicon-based plasma devices and hold promise for reconfigurable antenna systems.

A high gain, circularly polarized array antenna is proposed with low profile and compact size using T-shaped top loading, t-matching, and a reflector. Composed of 4 individual elements, the array has a -3-dB impedance bandwidth of 1.39% (1.564-1.586 GHz) and a 3-dB axial ratio beamwidth of 79° (-42°-37°) in measurement. The front-to-side ratio of the total realized gain pattern is 27.1 dB and the front-to-back ratio is 25.5 dB. The peak realized gain is 11.0 dBi in the forward (+z) direction. The proposed antenna is a good candidate for functioning as an anti-jam antenna in global positioning system, helping to block out jamming signals coming from the horizontal (90° and 270°) planes.

Reverberation chambers (RCs) were recently reported as a low-cost alternative to anechoic chambers (ACs) to perform radar cross-section (RCS) pattern measurements. The method consists i, using transmitting and receiving antennas pointing towards a target under test placed on a rotating mast. As a classical RCS characterization, the echo signal is analysed based on two measurements with and without the target in the RC. In the hypothesis of an ideal diffuse field generated in the RC, this signal difference appears as the echo signal hidden in a Gaussian noise. In case of a point-like backscattering target, observing this signal over a given frequency bandwidth allows the identification of the target response as a sinusoidal signal over this bandwidth whose period is related to the antenna-target distance measured from the measurement calibration plane positions. Therefore, the extraction of the magnitude of this sinusoidal signal requires a proper estimation of this distance. Furthermore, a sinusoidal regression processing relies on the approximation of a constant envelope over the selected frequency bandwidth, imposing some restrictions. In this paper, we introduce a two-step method that consists in identifying the most appropriate distance according to the target's orientation before estimating the magnitude of the sinusoidal signal. We highlight the improvement of RCS estimation on a point-like back-scattering target compared to the one-step procedure applied so far. In addition, it is shown that the analysis performed regarding the estimated distance provides a physical insight into the position of the equivalent backscattering point.

The present work proves by both simulation and experimental work that the most common empirical formulas available in the previous publications for the design of substrate-integrated waveguide (SIW) cavities are incorrect in most cases. Moreover, the present work provides correct and exact design equations that are examined by both simulation and experimental work. In planar circuit structures, rectangular waveguide and resonators are commonly integrated within a dielectric substrate to produce what is known as SIW structures. For ease of fabrication and embedding into the dielectric substrate, the closed (solid) side walls of the rectangular waveguides and resonators are replaced by metallic via arrays. The main concern of the present paper is to investigate the effects of such replacement on the performance of a SIW resonator through simulation as well as experimental work. The limiting constraints on the relative dimensions of such via arrays including the diameter of the vias and the spacing between them are numerically and experimentally investigated to ensure proper operation of the SIW resonator regarding the radiation loss due to leakage from the openings of the resonator side walls. The effects of the via array dimensions on the resonant frequency, radiation loss, and quality factor (Q-factor) of the resonator are evaluated. For this purpose, two models of the rectangular resonator embedded in the dielectric substrate are designed to operate at 10 GHz. The first model is an ideal box-shaped resonator of solid side walls whereas the other model is the conventional SIW resonator with via-array side walls. The two types of the substrate embedded resonators are fed through a microstrip line. The resonant frequency, losses, and Q-factor of the two resonator models are compared to each other taking the box-shaped resonator as a reference because of its ideal structure to evaluate the performance of a conventional SIW resonator. The two types of resonator are fabricated for comparison through experimental measurements. The empirical design equations that are commonly available in literature to calculate the effective dimensions of the SIW resonator are investigated by comparison with the exact simulation results and shown to be incorrect in most cases. More accurate and reliable design equations are proposed in the present work. The results of the proposed design equations are compared to the simulation results showing excellent accuracy and shown to be more reliable than those available in literature.

Low Energy (LE) devices for communication systems like Bluetooth, 5G New Radio (NR), etc. are most likely to be powered by a battery, however, the limitation of the utilization time of this power supply entails it to be handled in different way; one of them is using electromagnetic energy harvesting paradigm, which could be capable to supply the energy consumption of this device. In this research it is presented the design and implementation of a device for radio frequency energy harvesting in the Industrial, Scientific and Medical (ISM) band. As first step, field intensity measurements in ``Facultad de Informatica y Electronica'' (FIE) were performed by the utilization of NARDA SRM 3006 radiation meter, with the aim of determining the technology with highest radio frequency (RF) energy within the 2.4 GHz ISM band. After the analysis, the chosen was WiFi technology due to the massive implementation that exists in the surroundings. Therefore, the frequency of 2.45 GHz was selected as the center frequency for the design. The device was implemented using FR4 Epoxy glass material with a dielectric permitivity of 4.4 and a dielectric thickness of 1.6 mm. The device consists of 3 stages: i) Capturing energy using a microstrip patch antenna ii) Rectification using a coupling network followed by a rectifying circuit and iii) Energy storage using the method of harmonic balance and electromagnetic moment. Finally, harvesting measurements were carried out in FIE's laboratory; the RF energy of a WiFi router was harvested and at 10 cm a voltage of 510.6 mV was obtained, this level of voltage was capable of turning on a led diode demonstrating the functioning of the device.

The shielding effectiveness (SE) of electromagnetic shielding (EMS) clothing is primarily achieved through experimental testing, but this method comes with drawbacks such as high cost, extended time, and imprecise testing outcomes. In order to quickly and cost-effectively obtain the protective performance of clothing, this article proposes a fast estimation method for the local SE of EMS clothing, which can quickly estimate the SE in the chest and abdomen regions through human body shape parameters. Firstly, an elliptical conical surface model is established for the chest and abdomen regions according to the shape of the human body. Following the principle of calculus, a local SE solution method based on this model is constructed. Additionally, a model correction coefficient that takes into account the impact of holes and seams is offered. Finally, a rapid estimation method is established for the SE of the chest and abdomen regions of the clothing. Experiments are ultimately designed to validate the model. In conclusion, the estimated values of the model are in agreement with the measured values, and it exhibits fast and efficient performance. This paper provides a new way to rapidly estimate the SE of EMS clothing in local areas, and plays an important role in promoting the design, evaluation and related detection of EMS clothing.

Aiming to address the problem of radiation interference caused by pulse high current in the electromagnetic launcher's working process, this study presents a model for selecting materials for the protection of radiation sources and designing their topological structure. Initially, an analysis is conducted on the selection of materials and topology for the protective characteristics, considering factors such as protective effectiveness, production cost, structural rigidity, reliability, and mobility. Through shielding process, several factors influencing material selection are identified. Subsequently, weights and excitation functions are assigned to these factors to generate an applicability evaluation function of the protective materials, aligning with the test requirements. Next, three structures are defined for the test environment: inner shield, outer shield, and wrap-around shield, in accordance with the established protection topology. Using ANSYS, a three-dimensional simulation model is constructed, featuring a peak pulse current of 281.98 kA and an armature mass of 10 g. The shielding performance of materials with thicknesses of 3 mm, 5 mm, 7 mm, and 10 mm is analyzed. Simulation results demonstrate that the outer shielding structure and wrap-around shielding structure can achieve a magnetic induction strength of less than 0.5 T at approximately 6 mm thickness, validating the feasibility of the proposed model. This paper presents a method for addressing electromagnetic radiation protection from the electromagnetic launcher, ensuring the safety of personnel near the gas pedal and the stable operation of electronic components. The findings have significant implications for the future application of the system.

This study presents a compact, low-profile, and flexible fabric antenna specifically designed for on-body Wireless Body Area Networks operating within the Industrial, Scientific, and Medical (ISM) frequency band at a central frequency of 2.45 GHz. The proposed antenna employs a jeans substrate, with a dielectric constant ε_r = 1.67 and loss tangent tanδ = 0.025, which is 0.5 mm in thickness, allowing for its flexibility. The antenna incorporates slots on the patch and a Defected Ground Structure (DGS), with a total size of 36 × 55 × 0.6 mm³ (0.29λ_o x 0.45λ_o x 0.005λ_o mm³). To assess the antenna's flexibility, bending analysis was performed, while its performance was evaluated using a phantom model that simulates human tissue, comprising skin, fat, and bone, with respective thicknesses of 1 mm, 0.5 mm, and 4 mm. The final model of the antenna operates at a central frequency of 2.45 GHz, with an impressive bandwidth of 0.8 GHz. The proposed design maintains a high level of directivity, gain, and Reflection Coefficient (S₁₁) at the desired frequency, with values of 4.7 dBi, 3.6 dBi, and -41 dB, respectively. The Specific Absorption Rate (SAR) of the final antenna was measured on the above model and found to be 0.114 W/Kg for 1 g of tissue, which is well within the limits established by IEEE and FCC standards. Both the measured and simulated values of return loss and gain suggest that the proposed antenna is eminently suitable for body-worn applications.

Orbital angular moment modes (OAMs) have been proven to be promising resources for increasing communication capacity. To generate wideband and high purity OAM, we have proposed a transmitting metasurface with amplitude-phase dual control. The proposed unit cell is a novel split ring structure with upper and lower grating-like structures. By changing the direction angle and rotation angle of the split ring unit, the cross-polarization phase response and amplitude response of the unit are controlled respectively. The amplitude distribution of the metasurface array is calculated using Chebyshev synthesis method (CSM). We designed metasurface arrays with mode numbers l = 1, 2, 3 and it generated high purity OAM beams in the frequency band of 22--32\,GHz. Compared with traditional phase-control metasurface, amplitude-phase control surface can effectively improve the quality of OAM generation. The results have verified the accuracy of the proposed method, and the proposed method has potential applications in future communication system.

Permanent Magnet Synchronous Wind Generator (PMSWG) parameter identification method with improved operator genetic algorithm is proposed for the influence of perturbations caused by mechanical parameter changes on the dynamic performance of motor speed control system. Firstly, current with id=0 and id≠0 are injected into axis d respectively to design the fitness function. Through quantum coding, the genetic algorithm can obtain better population and fitness in the early stage, and find better solutions in the search space. At the same time, the cross method of two random numbers is used to make the cross variable not restricted in a range, which enhances the global search ability. Finally, the update strategy of hybrid mutation composed of Gaussian mutation and Cauchy mutation is introduced to ensure the global search ability of the algorithm, and the accuracy of the optimization results is improved. Experiments show that the proposed method avoids local optimization and achieves global optimization, which can further improve the convergence speed and identification accuracy of the algorithm.

The structure of the frequency diversity arc array (FDAA) is a circular arc, which can achieve fast scanning in all directions and large viewing angles. By selecting the appropriate array elements for FDAA to form an effective working array and designing the symmetrical logarithmic frequency offset, a more aggregated point-like beam pattern is obtained. However, due to the structural characteristics of FDAA, the anti-density weighting phenomenon is generated, which limits the application of FDAA in radar system for target recognition and tracking. In order to solve the problem of high sidelobe of FDAA caused by inverse density weighting, a method of FDAA with angle widening null guidance for sidelobe suppression is proposed in this paper. The linear constraint minimum variance (LCMV) criterion is used to set zero points at a fixed position in the direction of interference, so that the interference is in a null with a certain width. Through Matlab simulation, it is verified that this method has a certain effect on suppressing FDAA sidelobe interference.

In this article we present a ring Dielectric Resonator Antenna (DRA) fabricated on three-dimensional (3D) printed Acrylonitrile Butadiene Styrene (ABS) filament. The 3D printer offers antenna easy to fabricate and the possibility to design new antennas shapes more complex. The simulation performed using CST software 2020 shows that the proposed ring DRA has two resonance frequencies 23.5 GHz and 26.4 GHz with an obtained great gain 9.5 dB and 10.5 dB, respectively. A wideband about 42.4% was measured.

A combinatorial quantitative reconstruction method employing Subspace-based Virtual Born Iteration Method (SVBIM) along with a greedy compressive sensing algorithm, Sparse Reconstruction by Separable Approximation (SpaRSA) to solve the ill-posed inverse problem in microwave imaging is proposed in this paper. SVBIM makes use of the contribution of the variational induced current to arrive at a better estimate of the permittivity profile in each iteration. SpaRSA operates in the sparse domain and reduces the computational overload, thereby guiding the inverse problem towards a faster global optimum solution. The merger of these two algorithms helps to reconstruct breast profiles having high-permittivity tumour inclusions (ε = 60) with reduced error. The proposed reconstruction method is capable of extracting the salient information regarding tissue differentiation (permittivity and conductivity) and dielectric distribution of various tumour and fibroglandular inclusions within the object, dimensions, resolution, size, shape and coordinate localization of inclusions. In comparison to various methods reported in literature, the results obtained using the proposed method are highly encouraging. In the presence of 30 dB noise, the above-said imaging technique produces a significantly reduced permittivity error value of 0.47 in the reconstruction of tumour inclusions as against 0.85 and 0.71 in the case of TV norm and Re-weighted Basis Pursuit methods respectively. The experimental validation is carried out using a phantom having three inclusions of sizes 10 mm, 6 mm, and 3 mm. The inclusions have been localized successfully with errors of 0.089, 0.133, and 0.21, respectively.

A novel balanced-to-unbalanced (BTU) all-port reflectionless filtering power divider without loading additional absorptive branches at input and output ports is proposed in this paper. The proposed power divider includes two reflectionless filtering networks, four transmission lines, a phase inverter, and two isolation resistors. Unlike the existing filtering power dividers that require additional absorptive branches to be loaded at each port to achieve reflectionlessness at all ports, the proposed power divider achieves all-port reflectionlessness by embedding only two reflectionless filtering networks in the BTU power dividing circuit. Meanwhile, this reflectionless filtering network also introduces two transmission zeros located at the lower and upper sides of the passband, respectively, for high selectivity. To validate the proposed power divider topology, a 2.0-GHz BTU filtering power divider is designed and fabricated with a 3-dB filtering bandwidth of 40.1%. The 10-dB reflectionless bandwidth for the balanced port is 98.7% from 0.940 to 2.772 GHz and that for the unbalanced ports covers the entire measurement frequency from 0.5 to 3.5 GHz, achieving good all-port reflectionless characteristics.

In this paper, a low cross-polarization level, low radar cross section (RCS), conformal, ultrawideband, polarization-insensitive absorber utilizing sinusoidal periphery annular ring (SPAR) resonator based novel resistive metasurface is presented. The proposed absorber operates with more than 90% absorptivity over the frequency range 7.68 GHz-24.90 GHz encompassing X-, Ku- and major portion of K-bands. The absorber consists of two sinusoidal peripheries annular rings embedded with lumped resistors, placed on top of a 0.1 mm thin low cost FR-4 substrate which is supported by metal backed foam. The sinusoidal periphery on the annular rings improves the absorption bandwidth and miniaturizes the proposed structure. Cross-polarized reflected component from the absorber is also investigated and included in the estimation of absorptivity to validate that the proposed structure functions as an absorber and not as a reflective type polarization converter. An equivalent circuit analysis based on the transmission line model is also presented. Novelty of the proposed article's lies in the design approach for the proposed absorber in which flexibility is incorporated to choose unit cell geometrical parameters as per the limiting frequencies (upper and lower) of desired band along with some miniaturization aspects of the absorbing structure. Furthermore, 10 dB RCS reduction is discussed, and the formula is derived by including cross-polarized reflection component of the incident wave in estimation. The proposed absorber is validated through theoretical, simulation, and experimental studies for planar and conformal applications.

The separation of water droplets on the insulator umbrella surface is an important factor that increases the probability of flashover along the surface. Previous studies have only investigated the motion and deformation of water droplets on the horizontal insulator sample surface and their effect on flashover voltage. In actual composite insulators, the umbrella skirt surface is usually inclined at a certain angle. The influence of the umbrella angle on the motion law and flashover voltage of water droplets has not been fully studied in recent research. In this paper, focusing on the separated water droplet on insulator sample surfaces with different inclination angles, the motion modes and flashover characteristics of the water droplet are studied by using multi-physics finite element simulation and AC flashover experiment. The results show that the motion modes of water droplets changes with the inclination angle of the umbrella surface. The water droplet oscillates left and right under the AC electric field when the inclination angle is small. As the inclination angle increases, the oscillating trend of the water droplet weakens. When the inclination angle is large enough, the deformation of the water droplet shows two forms: sliding and stretching. As the inclination angle of the umbrella surface increases, the flashover voltage decreases, and the decreasing trend of the flashover voltage is greater when the inclination angle is larger.

This paper presents a small size M-shaped polygonal slot antenna for X-band satellite telemetry and Synthetic Aperture Radar (SAR) applications. The proposed antenna has been designed on a Roger RT-Duroid 5880 substrate. The reflection coefficient |S₁₁| of the proposed antenna covers the whole X-band from 6.63 GHz to 12.566 GHz. The proposed antenna is circularly polarized with axial ratio (AR) bandwidth that extends from 7.76 GHz to 8.58 GHz. The proposed antenna provides a simultaneous dual circular polarizations (RHCP and LHCP). The gain of the proposed antenna varies between 6.6 dBi and 9.4 dBi. The proposed antenna realizes an efficiency of 92%. The overall size of the proposed antenna is 17 x 16 x 0.508 mm³ (0.56λ₀ x 0.53λ₀ x 0.016λ₀). Therefore, it is suitable to be employed in satellite telemetry application from 7.9 GHz to 8.4 GHz especially for CubeSats that have limited surface area. Apart from that, this antenna finds its applications in SAR on small satellites from 9 GHz to 10 GHz, military, and RFID tag (tracking-equipment). It has been observed that the measurement results match the simulated ones. The proposed antenna design can be practically employed for the previously mentioned applications.