In this paper, a novel, highly isolated ultra-wideband multiple-input, multiple-output antenna design for indoor communication is proposed. The overall size of the antenna is only 36 × 36 mm², and it contains four monopole antenna units and a fan-shaped isolated structure. Each antenna cell is composed of a U-shaped patch element and a defected rectangular ground structure. The fan-shaped decoupling structure effectively absorbs coupling currents, significantly improving isolation. As a result, the proposed antenna system can cover the entire ultra-wideband and receive a resonant frequency of 2-11.08 GHz. The results demonstrate that the antenna's isolation is greater than 15 dB in the operating band. Furthermore, the antenna exhibits good radiation characteristics and reasonable envelope correlation coefficients.

This research presents a frequency reconfigurable antenna analysis for wireless applications using multiple light sources. The antenna is constructed on a Roger substrate with (44x28) mm² dimensions. The antenna comprises two parallel tuner arrangements in addition to a V-shaped radiating section. Two optical PIN photodiodes are connected to the two parallel monopole tuners, which serve as the antenna's switching component and are utilized to adjust the resonant frequency. These two PIN photodiode switches work in the 600-1050 nm wavelength range. To analyze the antenna performance, four different optical sources are used. They are white colour LED lamp, 650 nm optical fiber, red LEDs, and IR LEDs. In every case, the antenna performance analysis are carried out for all the four logic state of the switches (00, 01, 10, 11). Under white lamp test conditions, the antenna's maximum gain is 6 dBi, and when red LEDs are employed as the optical source, its maximum bandwidth is 21%. The antenna reconfigurable frequencies are 3.5 GHz and 5-5.8 GHz (5, 5.2, 5.5, 5.8 GHz).

To improve the beam collection efficiency (BCE) of the microwave wireless power transmission (MWPT) system while reducing the peak sidelobe level outside the receiving area (CSL) and system cost, this paper proposes a new subarray partition technique and a nonuniform sparsely distributed quadrant symmetric planar array (NSDQSPA) model. A particle swarm optimization algorithm based on multiple-objective with nonlinear time-variant inertia and learning factor improved particle swarm optimization (MO-NTVILF-IPSO) is also proposed. The one-step multi-objective subarray partition algorithm adopts dynamic weight and dynamic learning factor to carry out one-step optimization on the array element arrangement of the transmitting array. The optimization algorithm simultaneously optimizes two performance indicators: the ΔBCE, which represents the optimization accuracy for the BCE, and the α_ref, which represents the mean square error of the excitation amplitude before and after the subarray partition. Many simulation results show that the BCE is 94.91%, and the CSL is -13.41 dB when the transmitting array with an aperture of 4.5λ×4.5λ is divided into six subarrays. The simulation results further demonstrate that the proposed subarray division method is appropriate for the MWPT system and that the algorithm in this paper, when the array elements with the same excitation amplitude are divided for the planar transmitting array on the array model, and can guarantee relatively high BCE and relatively low complexity of the system feed network.

This paper proposes a hybrid cross-coupled filter that utilizes a coplanar waveguide (CPW) resonator and a hybrid electromagnetic coupling structure. The filter features a flexible and controllable position of the transmission zeros and a quasi-elliptical response. It is composed of two CPW structures etched within the upper metal surface of a second-order substrate-integrated waveguide (SIW) resonant cavity. By adjusting the dimensions of the two CPW structures between the SIW resonant cavities and the width of the inductive coupling window, the strengths of the electric and magnetic couplings can be easily controlled to achieve a controllable hybrid cross-coupling effect in order to adjust the position of the transmission zeros and ultimately to realize the third-order filter with quasi-elliptical response characteristics. Simulation and test results indicate that the filter has a center frequency of 4.55 GHz, a -3 dB bandwidth of 180 MHz, a relative bandwidth of 4%, an insertion loss of -0.9 dB in the passband, a return loss of over 15 dB, and two transmission zeros located at 4.4 GHz and 4.7 GHz, respectively. The filter has several advantages, including a simple structure, low insertion loss, small circuit size, good frequency selectivity, and flexible and controllable transmission zeros. These features make it suitable for use in 5G (sub-6 GHz) wireless communication systems.

The multifunctional metasurface offers a high degree of flexibility in manipulating electromagnetic waves. However, the majority of its functions are limited to the reflection or transmission space in a single band, restricting the utilization of electromagnetic information. This paper proposes a three-channel multifunctional frequency multiplexing coding metasurface based on the Fabry-Perot cavity principle. It consists of two layers of orthogonal metal gratings and a cross-shaped, oblique open loop structure in the intermediate layer. Simulation results reveal that at an incidence of 22 GHz, the polarization conversion and focusing functions of the transmitted wave are accomplished. Similarly, at an incidence of 31 GHz, the beam deflection function of the reflected wave is observed. Furthermore, at an incidence of 32 GHz, the radar scattering cross-section reduction function of the reflected wave is achieved. In addition to achieving high efficiency, miniaturization, and compactness, the proposed metasurface effectively enhances the spatial utilization of electromagnetic information. As a result, potential applications in multifunctional integrated systems, including wireless communication, sensing technologies, and radar systems, are vast.

Reconstructing a range profile from radar returns, which are both noisy and band-limited, presents a challenging and ill-posed inverse problem. Conventional reconstruction methods often involve employing matched filters in pulsed radars or performing a Fourier transform of the received signal in continuous wave radars. However, both of these approaches rely on specific models and model-based inversion techniques that may not fully leverage prior knowledge of the range profiles being reconstructed when such information is accessible. To incorporate prior distribution information of the range profile data into the reconstruction process, regularizers can be employed to encourage specific spatial patterns within the range profiles. Nevertheless, these regularizers often fall short in effectively capturing the intricate spatial correlations within the range profile data, or they may not readily allow for analytical minimization of the cost function. Recently, the Alternating Direction Method of Multipliers (ADMM) framework has emerged as a means to provide a way of decoupling the model inversion from the regularization of the priors, enabling the incorporation of any desired regularizer into the inversion process in a plug-and-play (PnP) fashion. In this paper, we implement the ADMM framework to address the radar range profile reconstruction problem where we propose to employ a Convolutional Neural Network (CNN) as a regularization method for enhancing the quality of the inversion process which usually suffers from the ill-posed nature of the problem. We demonstrate the efficacy of deep learning networks as a regularization method within the ADMM framework through our simulation results. We assess the performance of the ADMM framework employing CNN as a regularizer and conduct a comparative analysis against alternative methods under different measurement scenarios. Notably, among the methods under investigation, ADMM with CNN as a regularizer stands out as the most successful method for radar range profile reconstruction.

In this paper, the on-wafer S-parameter measurement of InP-Based HEMT devices up to 220\,GHz is presented. The calibration kits utilizing a CPWG structure are meticulously designed on an InP substrate. The corresponding structure for calibrating the reflection mechanism is designed in order to reduce the influence between the two ports during the calibration process and improve isolation. The TSVs process is employed to attain broadband load. The design concept of the calibration structure is discussed, and the simulation results up to 220\,GHz are provided for demonstration. The measurement results encompass frequency ranges of 0.2-66 GHz, 75-110 GHz, 110-170 GHz, and 170-220 GHz. Moreover, the test results obtained from different calibration methods for InP HEMT devices are compared and analyzed. By employing interpolation techniques, comprehensive S-parameter data for actual DUTs ranging from 0.2 to 220 GHz is successfully obtained. Furthermore, the intrinsic parameters C_gs is extracted from device test results, and various calibration methods are utilized for comparison. The extrapolated maximum current gain cut-off frequency f_T based on a -20 dB/decade slope in H₂₁ is determined as 252 GHz while the extrapolated device maximum oscillation frequency fmax calculated through the maximum stable gain (MSG)/the maximum available gain (MAG) and Umason approaches reaches up to 435 GHz.

Active magnetic bearings feature advantages of frictionlessness, low loss, and high reliability, making them extensively utilized in fields such as flywheel energy storage, aerospace, and beyond. However, conventional modulation strategies applied to digital control systems suffer from control delays, reducing current control precision and resulting in increased current ripple. To address the aforementioned issues, firstly, the operating principle of the active magnetic bearing drive system is analyzed. Based on hybrid systems theory, a mix logical dynamic model of the drive system is established by introducing auxiliary logical variables and auxiliary continuous variables to achieve three-level modulation. Secondly, integrating model predictive control theory, the established model is utilized as a predictive model to forecast and compensate for control delays in controlling current. Finally, a cost function is established based on the error between predicted current and reference current, and optimal control signals are generated to achieve precise control of the active magnetic bearings. The simulation results demonstrate that under light load conditions, the modulation strategy proposed in this paper reduces current ripple by 49.94% compared to traditional modulation strategies. Under moderate load conditions, the proposed modulation strategy reduces current ripple by 49.96%, while under heavy load conditions, it reduces current ripple by 49.99%. This validates the effectiveness of the proposed modulation strategy in compensating for control delays while retaining the three-level modulation scheme.

In challenging operational environments such as underground buildings beneath roadways, the reliability and performance of wireless power transfer (WPT) systems for electric vehicles (EVs) heavily hinge on the operating temperature of the magnetic couplers. Addressing this, this study introduces a novel approach employing heat sink and thermoelectric cooler technologies to mitigate temperature rise in magnetic couplers, which is particularly crucial for high-power applications. Utilizing ANSYS simulation, the study evaluates a WPT high-power application coil model with a total output power of 2 KW and an 18 cm air gap, with a 3.5 cm adjacent alignment to enhance thermal performance on both transmitter and receiver sides. Results demonstrate significant thermal enhancement, reducing the temperature of coils from 63˚C to 54˚C solely with the heat sink and further down to 48˚C with the combined implementation of both heat sink and thermoelectric cooler. These measures effectively dissipate heat from the coils into the surrounding air, ensuring system efficiency and stability while facilitating optimal functionality of system components.

A novel proposal for upcoming wireless applications introduces a dual-band, highly decoupled, and compact microstrip patch co-planar waveguide (CPW)-fed MIMO antenna. This low-profile antenna exhibits narrow wide-band performance across the frequency bands of 6.2 to 11.2 GHz, with dimensions of 20 × 20 mm³ on a standard FR4 substrate. Through integration onto a printed circuit board (PCB) measuring 20 × 20 mm², the antenna configuration is expanded to a 4 × 4 MIMO arrangement. Individual antennas within this setup maintain a significant isolation of around 20 dB in the absence of a decoupling mechanism. Fabrication of the designed four-port antenna allows for practical measurement of various antenna parameters. The measured results closely align with simulated outcomes, encompassing S parameters, far-field patterns, and MIMO characteristics such as envelope correlation coefficient, channel capacity loss, and total active reflection coefficient. These results suggest that the antenna design presented in this study holds promise for future wireless applications.

This research provides a unique design of a terahertz-frequency metamaterial absorber. The absorber shows resonance at frequency 5.01THz where the peak absorption is 99.5%. A staggering quality factor of 125.25 is also discovered. Since the radiation is non-ionizing, the metamaterial absorber can function as a refractive index sensor and can be used for sensing applications. To support the chosen design parameter values, parametric analysis was performed. The resonance mechanism has been clearly explained using the surface current distribution plot, and the metamaterial nature of the sensor has also been justified using the impedance plot, followed by the plot showing the permeability and permittivity at the resonance frequency. By detecting changes in the refractive index of the surrounding medium, the proposed sensor finds application in detecting the percentage of water and percentage of methanol in alcohol solution. Methanol and water are two prominent contaminants of alcohol. It can detect the percentage of water in alcohol with a sensitivity of 2.105 THz/RIU and can detect percentage of methanol in alcohol with a sensitivity of 1.999 THz/RIU. This work can inspire future research on using THz metamaterial absorbers for quality assessment of food products and beverages.

Reliably modeling vulnerable road users (VRUs) such as motorcyclists in the virtual environment is indispensable in developing over-the-air (OTA) validation test methods. However, there are still challenges arising from many possible variations of VRUs, which may participate in the traffic scenarios. Therefore, it is essential to model them precisely and demonstrate consistency between virtual evaluation and reality. To achieve this goal, the VRUs must be modeled based on their backscattering behavior which can be prepared based on high-resolution (HR) radar cross section (RCS) measurements. This work presents the backscattering behavior of motorcyclists as one of the critical VRUs in traffic scenarios. The extracted model of a motorcyclist is analyzed and compared based on HR-RCS measurements with different motorcycle variants. This evaluation is a prerequisite for developing a realistic model of VRUs and ensuring an adequate level of accuracy.

In this letter, a TE₀₁ operation of a multilayered Substrate Integrated Waveguide (SIW) is presented. To enable the propagation of this typically unsupported mode, the SIW is integrated with feeding layer and with an Electromagnetic Band Gap (EBG) structure, exciting and confining the field within the proposed waveguide structure. The EBG is simply stacked on top and bottom of the proposed structure, allowing for ease of manufacturing. The overall proposed structure is simulated and measured, and the results indicate very low insertion loss in the passband of the waveguide.

Outer rotor coreless bearingless permanent magnet synchronous generator is a complex and strongly coupled nonlinear system. The stable suspension and voltage of generator are always the focus and difficulty of research. The fuzzy dynamic sequential model predictive torque control method based on prediction error compensation is proposed. Firstly, the basic structure and working principle of the outer rotor coreless bearingless permanent magnet synchronous generator are introduced in this paper, and the mathematical model of voltage and suspension force is established. Secondly, the mathematical model is carried out to obtain the prediction equation, and the prediction error compensation is carried out to the prediction equation, and then the number of the first output voltage vectorsis determined by fuzzy controller. Finally, the designed control system is simulated and experimentally studied. The simulated and experimental results show that this control method can obtain good voltage and suspension response, and the outer rotor coreless bearingless permanent magnet synchronous generator has good dynamic performance and stability.

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.