In order to improve the classification performance of Polarimetric Synthetic Aperture Radar (PolSAR) image by synthesizing various polarimetric features, a supervised manifold learning method is proposed in this paper for PolSAR feature extraction and classification. Under the umbrella of tensor algebra, the proposed method characterizes each pixel with a feature tensor by combining the high-dimensional feature information of all the pixels within its local neighborhood. The tensor representation mode integrates the polarimetric information and spatial information, which is beneficial for alleviating the influence of speckle noise. Then, the tensor discriminative locality alignment (TDLA) method is introduced to seek the multilinear transformation from the original polarimetric-spatial feature tensor to the low-dimensional feature. The label information of training samples is utilized during feature transformation and feature mapping; therefore, the discriminability of different classes can be well preserved. Based on the extracted features in the low-dimensional space, the SVM classifier is applied to achieve the final classification result. The experiments implemented on two real PolSAR data sets verify that the proposed method can extract the features with better stability and separability, and obtain superior classification results compared to several state-of-the-art methods.

In this work, a low-profile and flexible antenna operating in the ISM (2.4-2.4835) GHz band for bio-telemetry applications is presented. This antenna is designed on two flexible substrate materials: Roger RO3003 with a thickness of 0.254 mm and jeans fabric material with a thickness of 0.7 mm, of an overall foot print of 20 × 30 mm². The deformation bending of the designed antenna in two different cases is studied. The designed antenna is backed by a 3 × 3 artificial magnetic conductor (AMC) array structure, which resulted in the final design configuration. The antenna is backed by an AMC array structure to achieve a lower specific absorption rate (SAR) as well as high gain when it is mounted on biological tissue. For validation, the antenna is fabricated on two flexible substrate materials and then measured in free space as well as on four different parts of the realistic human (chest, back, arm, and leg) body with and without AMC structure. Furthermore, the SAR is measured on cSAR3D flat. Finally, for reliable communication, the link margin is calculated.

The process of smart antenna synthesis involves the automatic selection of the optimal antenna type and geometry in order to enhance antenna performance. A model for intelligent antenna selection employs an optimizable K-nearest neighbors (KNN) classifier to determine the optimal antenna choice. To optimize the utilization of different learner types, the geometric parameters of the antenna are presented as the final step prior to the construction of the ANFIS model, which involves the integration of five distinct primary learners. The classification of three distinct types of antennas, namely helical antenna, pyramidal horn antenna, and rectangular patch antenna, is performed using an optimizable K-nearest neighbors (KNN) classifier. Additionally, an ANFIS approach is employed to determine the optimal size parameters for each antenna. The accuracy is used to evaluate the performance of an Optimizable KNN classifier, whereas Mean Squared Error and Mean Absolute Percentage Error are used to evaluate the performance of an ANFIS. The proposed technique demonstrates high performance in parameter prediction and antenna categorization, achieving a Mean Absolute Percentage Error of less than 3% and an accuracy exceeding 99.16%. The recommended methodology holds significant potential for widespread application in the development of practical smart antennas.

An optimal blend of relatively high frequency and effective atmospheric penetration renders the X-band a versatile selection for a wide range of applications. Hence, metamaterial absorber and frequency selective surface (FSS) as a band-stop filter and shielding element play a significant role in X-band. This article proposes a cost-effective, wide oblique and polarization-insensitive metamaterial, whose applications as an absorber and FSS having band-stop characteristics for X-band are explained. The isotropic unit cell of the proposed metamaterial is designed by an array of two subunit cells, where one is the 90˚ rotated version of the other with diagonal symmetry. Equivalent circuits of both subunit cells and array structure are systematically designed and analyzed, which provides scope for future modification according to the required frequencies. The proposed absorber provides three absorption peaks and absorptivity of more than 90% up to 60˚ oblique incidence angle. A good agreement between experimentally measured and simulated results is observed. For the use of the structure as FSS, it has been optimized to provide band-stop characteristics precisely for the X-band up to a wide oblique incidence angle. The proposed design can be used as an absorber, band-stop filter, reflector, and shielding element for the X-band.

The application scenarios of near-field focusing metasurfaces usually require scanning the target area. Passive metasurface requires a turntable to complete scanning due to its limited functionality. The active metasurface typically has a high cost because it needs to load PIN diodes. To address this issue, the article introduces a 1-bit reconfigurable metasurface that can achieve multi-focus tunability under fixed polarization through a rotating array. The 1-bit polarization-independent metasurface unit consists of three layers of metal. The top layer of the unit consists of three rectangular patches in the X-direction, the middle layer is a cross-shaped patch structure, and the bottom layer is a metal ground. The cross-shaped structure in the middle layer can easily provide the 1-bit reflection phase required for two orthogonal polarizations independently. Using a vertically polarized horn to illuminate the metasurface, the top layer's X-direction rectangular patches do not provide phase for vertical polarization. By rotating the array where the cross-shaped patches are located by 90°, the phase shift provided can achieve two focal points. On this basis, rotate the upper array by 90°, making the rectangular patches change from the X-direction to the Y-direction. Meanwhile, the current of the cross-shaped patches is blocked under vertical polarization illumination. By changing the upper rectangular patches, a third independent phase can be provided. After size optimization, a third focus can be formed. The proposed 1-bit focusing-adjustable metasurface array has a simple structure, low cost, and enhanced utilization rate of the metasurface array. It has a high application prospect in projects such as microwave imaging.

The Stochastic Reduced-Order Models (SROM) is a non-embedded uncertainty analysis method that has the advantages of high computational efficiency, easy implementation, and no dimensional disasters. Recently, it has been widely used in the field of EMC simulation. In the process of optimizing electromagnetic protection design, the worst-case estimation value is an extremely important uncertainty quantification simulation result. However, the SROM has a large error in providing this result, which limits its application in the field of EMC simulation prediction. An improved SROM based on the Radial Basis Function (RBF) neural network algorithm is proposed in this paper, which improves the fitness function in the genetic algorithm center clustering process and constructs an RBF neural network model to obtain accurate worst-case estimation results. The accuracy improvement effect of the algorithm proposed in this paper in worst-case estimation is quantitatively verified by using a parallel cable crosstalk prediction example from published literature.

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.