In this paper, an antipodal Vivaldi antenna (AVA) with lower cutoff frequency is proposed based on spoof surface plasmon polaritons (SSPPs) and corrugated edges. Firstly, the gradient slots are etched on the external edges of two radiation arms of the conventional antipodal Vivaldi antenna. As a result, the cutoff frequency at the low frequency side will decrease slightly because the surface current path of the antenna is increased. More importantly, the SSPPs structure with identical units is etched on the inner side of two radiation arms, resulting in a large reduction of the cutoff frequency for the larger propagation constant of the SSPPs structure compared with radiation arms of the conventional antipodal Vivaldi antenna. Additionally, SSPPs structure on the stripline ensures good momentum matching and mode matching between quasi-TEM mode and SSPPs mode. Besides, to improve the gain at the high frequency region of the operation band, the introduced SSPPs structure on the inner side of two radiation arms is further optimized by varying groove depths. Experimental results demonstrate that the designed antipodal Vivaldi antenna exhibits a good radiation performance with a low cutoff frequency of 2.8 GHz and a maximum gain of 9.3 dBi.

The primary focus of this paper is to evaluate the channel capacity of a Terahertz (THz) communication system using a Multiple Input Multiple Output (MIMO) technique. By deriving mathematical expressions for channel capacity and considering practical constraints, the paper provides insights into the performance of such systems under various conditions. The channel model used in this work accommodates the channel accuracies and transceivers constraints. To validate the proposed channel capacity, some simulations by taking into account deferent parameters namely SNR (Signal to Noise Ratio), MIMO channel Matrix size and distance between transmitter and receiver are performed. These simulations are carried out for 3 cases which are: (1) Channel State Information CSI is known to both transmitter (Tx) and receiver (Rx), (2) CSI is known to Rx but unknown to Tx, (3) CSI is unknown to both Tx and Rx. In this study, we introduce a mathematical formulation for a communication channel tailored for Terahertz (THz) applications. Using this channel model, we analyze the capacity of the THz channel. The suggested research has the potential to be applied in the design and enhancement of Terahertz (THz) wireless communication systems, aiding in the advancement of robust and high-capacity wireless networks that can fulfill the requirements of contemporary multimedia applications.

In this paper, we give an analytical demonstration of electromagnetic induced transparency (EIT) resonance by a simple photonic device consisting of two grafted resonators (metamaterials of type Epsilon Negative Gauchy (ENG)) of lengths d₂ and d₃. Then, we study theoretically the transmission spectrum and the dispersion relation of periodic photonic comb-like waveguides system built of periodic segments of length d₁ (of right-handed material). The electrical permittivity, ε, of the two asymmetric resonators with lengths d₂ and d₃, depends on the frequency of the incident waves (ENG material). The presence of geometrical (ENG resonators) defects inside the perfect structure creates the defect modes inside the band gaps. Consequently, we demonstrate the existence of two filtered frequencies. This structure can be used as a new photonic filter in the microwave range with an important quality factor and a high transmission rate.

Planar feedback micro-nanoscale cavities, shaped by advances in nanofabrication, have revolutionized laser technology, giving rise to chip-scale, low-threshold lasers with wide-ranging applications, spanning from atmospheric investigation to incorporation intocentral devices such as smartphones and computer chips. The complicated designs of these cavities, shaped by the physics of periodic and quasiperiodic structures, empower efficient manipulation of light-matter interaction and coherent light coupling, minimizing losses. This review thoroughly explores the underlying concepts and crucial parameters of planar feedback microcavities, shedding light on the photophysical behavior of recent gain materials pivotal for realizing optimal lasing properties. The examination extends to photonic crystal bandgap (PhC BG) microcavity lasers, specifically with periodic and quasiperiodic architectures. In-depth assessments probe into the principles and designs of each architecture, exploring features such as wavelength selectivity, tuneability, lasing patterns, and the narrow linewidth characteristics inherent in distributed feedback (DFB) microcavity lasers. The review highlights the intriguing characteristics of non-radiative bound states in the continuum (BIC) within periodic architectures, emphasizing trends toward high-quality factors, low thresholds, and directional and vortex beam lasing. It also explores the nascent field of Quasiperiodic (QP) microcavity lasers, addressing challenges related to disorder in traditional periodic structures. Comparative inquiries offer insights into the strengths and limitations of each architecture, while discussions on challenges and future directions aim to inspire innovation and collaboration in this dynamic field.

A multiple antenna placement system analysis for the improvement of efficiency and capacity for inter and intra vehicular communication is proposed in this article. Four antennas are placed in the four locations of the vehicular body which includes roof, side mirror, rear screen, and dashboard. The constituted antenna occu-pying the dimension of 40×38.5×0.2 mm³ on flexible substrate material of photo paper and the bending analysis of the model as per the conformal nature on vehicular body is also analyzed and presented in this work. The received power from each receiving antenna response with respect to the transmitter has been analyzed. The chan-nel capacity with respect to the antenna position for V2V communication is analyzed in different areas and in different environmental conditions.

This paper presents an efficient and stable interpolation method for calculating two-dimensional periodic Green's function and its gradient. The method consists of two steps: constructing an interpolation table in the first step and using linear interpolation to extract the desired Green's function from the interpolation table in the second step. In the construction of the interpolation table, several properties of the two-dimensional periodic Green's function are fully utilized, which minimize the size of the interpolation table. When the elements in the interpolation table are computed, all possible singular terms are removed, ensuring that the interpolation function maintains high linearity even under extreme skew periodic grids. This means that linear interpolation can guarantee sufficient accuracy. Numerical results demonstrate effectiveness of the proposed method, making it suitable for combining with numerical methods for electromagnetic field calculation and analysis of periodic structures.

A reactive power shielding structure working under 150 kHz for small electronic equipment was proposed to reduce the electromagnetic leakage of WPT system. First, the model of LCC-LCC compensation circuit was established. By ensuring transmission efficiency, a comprehensive analysis of nine sets of computational data results was conducted to select the scheme with the best shielding effect. The experimental results showed that the magnetic flux density attenuation was 27.82% at 41 mm transmission distance from the center under the optimal structure of 3 rings and 7 turns, inner diameter of 23 mm and outer diameter of 35 mm. The transmission efficiency can reach 76.73%, which is only 1.32% lower than the situation without shielding. The proposed reactive power shielding structure can significantly reduce the magnetic flux density in the external area of the WPT system without affecting the transmission efficiency of the system.

This paper presents a novel bandpass filter with reconfigurable bandwidth or transmission zeros. The proposed filter is based on a multiple-mode stub-loaded resonator. Three PIN diodes are utilized as switching elements to achieve four switchable operating states. The measurement results indicate that the 3 dB fractional bandwidth (FBW) of the filter can be varied from 32.3% to 70% at the centre frequency of 2.2 GHz, and the stopband attenuation is higher than 35 dB. The filter size is only about 0.28λ_g×0.19λ_g.

A circular antenna array with omnidirectional mode and 360° continuously directional beam-scanning mode operating in 5G indoor communication band is reported. The proposed circular antenna array is composed of 16 subarray elements, and each element consists of two back-to-back E-shaped patch antennas with a differential feeding network. The beam-scanning mode is achieved by controlling the exciting amplitudes and phases of consisting subarray elements, which is optimized by using the extended method of maximum power transmission efficiency, so as to guarantee the maximum possible gain value. The operating frequency of the circular array covers 3.3-3.6 GHz. The omnidirectional gain is about 4.7 dBi, while the directive gain reaches 16 dBi with 360° continuously beam-scanning performance and very slight gain fluctuation in the azimuth plane. The comparison with other state-of-the-art designs shows that the proposed circular array has both higher directional and omnidirectional gain values.

Parity-time (PT) reversal symmetry, as a representative example in the field of non-Hermitian physics, has attracted widespread research interest in the past few years due to its extraordinary wave dynamics. PT-symmetry enables unique spectral singularities, including the exceptional point (EP) degeneracy where two or more eigenvalues and eigenvectors coalesce, as well as the coherent perfect absorber-laser (CPAL) point where laser and its time-reversal counterpart (i.e., coherent perfect absorber) can coexist at the same frequency. These singular points not only give rise to new physical phenomena, but also provide new plausibility for building the next-generation sensors and detectors with unprecedented sensitivity. To date, investigations into EPs and CPAL points have unveiled their great potential in various sensing scenarios across a broad spectral range, spanning optics, photonics, electronics, and acoustics. In this review article, we will discuss on going developments of EP- and CPAL-based sensors composed of PT-synthetic structures and offer a glimpse into the future research directions in this emerging field.

A bidirectional inductive power transfer (BIPT) system of full-compensated series-series (SS) topology with full bridge converters on both primary and secondary sides is analyzed in this paper. The steady-state electrical characteristics of the BIPT system under triple-phase-shift control are obtained, based on which, the conditions for achieving the maximum transfer efficiency of the intermediate circuit and zero voltage switching of all switches are derived. Triple Phase-Shift Control (TPSC) strategy was proposed for the control of the two inner phase shifted of the primary and secondary side full bridge converters and the fundamental excitation voltage phase shift, which achieved the maximum transfer efficiency of the intermediate circuit and zero voltage switching of all switches. The proposed control method was verified through simulation. The results showed that the control strategy can realize the bidirectional energy transfer of the IPT system, the efficiency optimization of the intermediate link, and the zero-voltage turn-on of all switching devices under various load conditions.

This article proposes a versatile Multiple Input Multiple Output (MIMO) antenna designed for contemporary wireless systems spanning frequencies from 3 to 20 GHz. It serves applications such as 5G mobile, WiFi, WiFi-6E, X-band, partial Ku, and K-band. The original single-element antenna evolves into a 4 × 4 MIMO configuration with optimized ground plane modifications for enhanced performance. A decoupling structure achieves over 20 dB isolation between inter-elements. The feeding structure, featuring a gradually changing design connected to the antenna's radiating structure, achieves wide bandwidth characteristics. This is further improved by a partial ground structure and slots on the radiating element. The lower frequency band of 3 to 7 GHz is attained with a rectangle-shaped radiator, while semi-circular microstrip lines atop the radiator enable the higher frequency bands of 8 to 15.4 and 18.7 to 20 GHz. The slots and ground structure enhance impedance bandwidth, and semicircles improve the radiation pattern. The MIMO antenna demonstrates measured peak gains of 4.4 dBi at 3.5 GHz, maintaining a radiation efficiency exceeding 80%. Validation through metrics like ECC, DG, CCL, and TARC confirms strong agreement between simulated and experimental results, positioning the MIMO antenna as a robust choice for various wireless communication applications.

Usually inactive or also known as thinned elements are used to simplify the array design complexity by turning off some of the active elements in uniformly filled arrays. Consequently, the far-field radiation characteristics such as sidelobe level, beamwidth, and directivity may be negatively changed if no optimizer is used. Further, these radiation characteristics may be unavoidably deteriorated when the main beam is scanned to new directions other than the referenced broadside direction. In this paper, an efficient optimization method based on the genetic algorithm and a dynamic deactivation method is proposed to randomly deactivate a number of array elements to minimize the peak sidelobe level and at the same time maintain the array directivity undistorted, while scanning the main beam. The deactivation method chooses optimally the suitable number of elements and their locations that need to be deactivated such that the resulting radiation characteristics positively change according to the specified cost function. Also, the proposed scanned array uses binary coefficients to activate and deactivate the array elements, thus, the feeding network of the proposed array is very simple, and it can be easily implemented in practice. Through extensive simulation results, we show that the proposed optimization method has good performance under wide range of scanned main beam directions. It is also found that the number of deactivation elements (i.e., the optimization variables) increases with larger scan angle.

The generalized sidelobe cancellation (GSC) is a commonly used adaptive beamforming technology, which can be used in antenna arrays. Due to the error of the direction of arrival of the received signal and the spacing error of the received array elements, the signal received by the array antenna has a mismatch of steering vectors, which leads to that the GSC method cannot accurately aim at the expected signal and suppress the interference signal. In order to improve the robustness of GSC algorithm, a new adaptive beamforming algorithm named SGSC (Sequential Quadratic Programming-Generalized Side Lobe Cancellation) is proposed in this paper. In this method, firstly, the mismatching expected signal steering vector is corrected by the stepwise quadratic programming, so that the auxiliary antenna can effectively block the expected signal. Then, the optimal weight vector is obtained by combining the corrected steering vector with the GSC, so that the expected signal components of the auxiliary antenna and of the main antenna can be avoided from being cancelled due to mismatch errors. Finally, the simulation results based on MATLAB show that the new algorithm can point the desired signal more accurately and suppress the interference signal more obviously in the presence of mismatch error, which shows the effectiveness of the method.

This paper proposes a UHF-band microwave sensor for solid material detection based on a tweaking electric field coupled (ELC) resonator. The microwave sensor operates at a low resonant frequency of 0.82 GHz to characterize solid materials with a permittivity range of 1-9.8. The location of the sensing area is determined based on the surface of the resonator with the highest electric field. The permittivity of the sample is determined based on perturbation theory by observing the frequency shift relative to changes in the permittivity of the sample placed in the sensing area of the proposed sensor. From the measurement process, the proposed sensor has a normalized sensitivity (NS) of 1.49%, frequency detection resolution (FDR) of 0.012 GHz, and an average accuracy of 96.72%. This work has a significant contribution and can be recommended for several applications including the pharmaceutical, biomedical, and materials industries.

This paper presents the design of conformal microstrip antennas wrapped around on a rocket cylinder. These antennas should exhibit favorable S₁₁-parameter values within the desired radio frequency range and an omnidirectional radiation pattern. Given their external placement on rockets, the challenge in this context is to ensure heat resistance. Two types of conformal microstrip antennas are developed to address this issue: one features an 8x1 array of rectangular patch (RP) elements, and the other consists of a single long rectangular patch (LP) element. Each antenna is wrapped around the rocket cylinder, with the patch array elements tailored to match the cylinder circumference to achieve an omnidirectional radiation pattern. Both antennas operate at a resonant frequency of 2.44 GHz and are constructed using RT/duroid 5880, a flexible material with a low dielectric constant. The antennas designs are assessed through computer simulations, followed by fabrication and measurements to analyze their performance against simulation results. The results indicate that the conformal RP antenna displays an S₁₁ value of -24.512 dB at the center frequency of 2.445 GHz featuring a 48 MHz bandwidth, while the conformal LP antenna discloses an S₁₁ value of -16 dB at the center frequency of 2.44 GHz having a wider bandwidth of 55 MHz. Both of the conformal RP and LP antennas exhibit an omnidirectional radiation pattern with a maximum gain of 6.13 dB and 7.21 dB, respectively. Following simulation and testing results, the antennas can tolerate temperatures up to 71.8˚C during flight tests. Although temperature variations trigger slight frequency shifts, these deviations are insignificant. Finally, the measurement results agree with the simulation ones.

This paper presents an innovative high gain multiple-input-multiple-output antenna featuring a compact circular shape, enhanced by strategically positioned slots, slits, and defected grounds created by etching multiple iterations of circle inserted with triangle shape. The investigation thoroughly explores the various traits and properties exhibited by the antenna. The antenna design harmoniously incorporates two radiating elements shaped in circles, positioned 16 mm apart from their centers, and has been physically constructed using an FR4 substrate. Enhancing the antenna's bandwidth and gain requires the implementation of slots with fractal patterns on the ground with a precise edge-to-edge separation of 2.5 mm. The placement of the antenna elements at a 16 mm distance guarantees an isolation level exceeding 15 dB consistently throughout the entire wideband frequency range. The dimensions of the compact MIMO antenna are tailored to be 1.12λ × 1.8λ × 0.091λ (20 × 32 × 1.62 mm³). In this study, the circular patch MIMO antenna with a fractal DGS resonates precisely at 16.903 GHz. It showcases an impressive impedance bandwidth spanning 2.027 GHz, ranging from 15.946 GHz to 17.973 GHz. It exhibits a reflection coefficient of -43.82 dB and achieves an observed gain of 6.25 dBi. The observed results include a minimal envelope correlation coefficient (<0.025) and a substantial Diversity Gain (>9.89). The measured results mirror the simulated outcomes, affirming the effectiveness of the wideband, high-gain antenna design. Its bandwidth and gain are well-suited for Satellite Communications particularly in downlink applications, enabling faster data transmission rates.

Dividing large planar arrays into several subarrays and then turning off some of them reduces the complexity (cost) of the system significantly. In this paper, two optimization stages for the formation of planar subarrays and the removal of some of them are proposed. The first optimization stage improves the pattern of the original planar array after dividing it into a set of rotational square and rectangular subarrays. In the second optimization stage, it works to remove some of the subarrays completely or partially, depending on new fractal structures derived from the conventional Sierpinski carpet structure. The proposed fractal-thinned planar array is based on amplitude-only excitation, i.e. the phases of the elements are set to zero. To execute the optimization steps above, a genetic algorithm (GA) is used. Some determinants are included in the optimization process to maintain the properties of the desired pattern. Simulation results showed the effectiveness of the proposed optimization method in achieving almost the same performance in both stages of optimization.

As one of the most basic electric quantities in the power system, voltage plays an important role in many fields such as condition monitoring and fault diagnosis. The construction and development of the smart grid cannot be separated from the reform and progress of the advanced sensing and measurement technology. Noncontact voltage measurement technology, as one of the important technologies, has many advantages such as no electrical contact, low insulation requirements, easy installation, and great potential in improving the panoramic perception ability of the power system. In this paper, a noncontact measurement method of the power line voltage based on capacitive coupling principle is proposed, which realizes the reliable measurement of the line voltage waveform. First, the principle of the noncontact voltage measurement method is introduced, which mainly includes self-calibration and online measurement of the sensor. The high-frequency voltage signal is injected into the capacitive coupling network of the sensor to implement the self-calibration of the sensor. Then, the digital integration method is used to integrate the output signal of the sensor to measure the line voltage waveform. Second, the noncontact voltage sensor prototype and the signal processing circuit are designed. Finally, the test platform of the line voltage measurement is built, and the measurement test of 220 V/50 Hz line voltage waveform is carried out. The test results show the relative amplitude error of the voltage measured by the sensor is less than 2.5%, the maximum phase error less than 2° at 50 Hz, and the linearity better than 0.5%. The frequency response experiment shows that the system has almost constant gain in the frequency range of 50-1800 Hz, and the phase error reaches a maximum of 2.8° at a frequency of 1800 Hz.

Surface Plasmon Resonance (SPR) serves as a crucial optical technique in the realm of chemical sensing. Under specific conditions, the reflectivity of a thin metal film exhibits an exceptional sensitivity to optical changes in the medium on one side. In this investigation, we propose and simulate a plasmonic sensor incorporating a silicon nitride grating with Ag layers for the detection of solution and gas at an optical communication wavelength of 1550 nm. In both cases of the surface diffraction-grating, there is a notable enhancement in angular sensitivity compared to conventional prism-coupled configurations. Simulations, employing rigorous coupled wave analysis (RCWA), highlight that the suggested sensor, optimized in design parameters, offers notably superior sensitivity, a lower detection limit, and a higher figure of merit (FOM) than existing grating-based SPR sensors. This implies the potential realization of refractive index sensors with a high figure of merit through such streamlined and compact configurations.