In this article, a fractal slotted metamaterial inspired multiband antenna for wireless communication applications is presented. The proposed structure incorporates the fractal formation of a radiating patch attached with metamaterial SRR cell and rectangular slotted partial ground plane to cover multiple wireless standards. The antenna is printed on FR4 epoxy substrate material having the thickness of 1.6 mm and relative permittivity of 4.4. The antenna has compactness in size as 37×22×1.6 mm³ and achieves five wireless communication modes, including S band (2.4 GHz; WLAN: IEEE 802.11g), S band (3.65 GHz; WiMAX: IEEE 802.16e), C band (5.0/5.8 GHz; WLAN: IEEE 802.11a/j), X-Band (Satellite communication, radar, terrestrial broadband, space communication), 5G NR bands (n41: 2.496-2.690 GHz, n46: 5.15-5.925 GHz, n47: 5.855-5.925 GHz, n53: 2.483-2.495 GHz, n102: 5.925-6.425), and Lower Ku band (Molecular rational spectroscopy). The antenna also showcases consistent radiation characteristics, gain, and efficiency across resonant bands crucial for obtained resonant bands regarding multi-standard wireless applications. It attains an optimized peak gain of 4.38 dBi and a radiation efficiency of 86.23%.

This article proposes an 8-port MIMO antenna based on double-negative metamaterial Split Ring Resonators (SRRs) for three-dimensional (3D) non-planar applications, such as hotspots. The antenna features eight radiators arranged orthogonally to each other, placed in two perpendicular planes, operating at 3.5 GHz. Each resonator incorporates six embedded SRRs to enhance the metamaterial behavior, achieving a 40% size reduction compared to a conventional disc monopole at the same frequency. Simulated and measured results demonstrate excellent performance for MIMO applications, with Envelope Correlation Coefficient (ECC) values below 0.001 and Diversity Gain (DG) around 20 dB. The Total Active Reflection Coefficient (TARC) bandwidth is approximately 930 MHz at the -10 dB threshold. The S-parameters indicate excellent electromagnetic isolation between radiators exceeding 20 dB, and a very low cross-polarization level below -30 dB. However, the main limitation of this design is a reduction in gain, an expected result.

This paper presents a multifunctional antenna with high isolation for interweave and underlay cognitive radio (CR) applications. The proposed antenna consist of an ultra-wideband (UWB) antenna (ANT1) for sensing and communication in UWB spectrum range and a frequency reconfigurable antenna (ANT2) for communication over frequency ranges from 3 to 3.7 GHz and 3.8 to 5.6 GHz. The proposed antenna is designed on an FR-4 substrate 50 × 65 × 1.6 mm³ with a shared ground plane. A square slot and a rectangular stub is introduced in the ground plane to achieve -10 dB wide impedance bandwidth and good isolation over the frequency range of 1.8 to 12 GHz. An underlay CR operation is attained with a UWB ANT1 with reconfigurable band notch of 2.76 to 3.7 GHz by introducing a U-shaped slot. The interweave operation is obtained by incorporating ANT1 and ANT2 in a same substrate. ANT1 without notch band is used for sensing spectrum and ANT2 with reconfigurable frequency is used for communication. The proposed antenna attains both interweave and underlay operations with inter-port isolation greater than 17 dB all over the proposed UWB and communication band.

To solve the problem of poor control performance of internal permanent magnet synchronous motors (IPMSM) due to parameter perturbations and external perturbations when adopting mode-free sliding mode control (MFSMC) algorithm, a double-closed-loop model-free super-twisting terminal sliding mode control (MFSTTSMC) algorithm of IPMSM based on third-order super-twisting observer (TOSTO) is proposed. Firstly, according to the new model-free control (MFC) algorithm, an ultra-local expansion model of IPMSM speed-current double closed-loop is established. Secondly, based on the ultra-local expansion model, a double closed-loop MFSTTSMC is designed to achieve global rapid convergence of system state errors. At the same time, a TOSTO is designed to estimate the disturbance in real time and carry out feedforward compensation, which enhances system robustness. Finally, the viability and superiority of the proposed control algorithm is demonstrated through simulation and experiments.

Through the analysis of experimental data, it is found that the optimal communication frequencies of mine tunnels with different cross-sections are different. These optimal operating frequency bands (580-600 MHz, 806-826 MHz, 1427.9-1447.9 MHz, 2401.5-2481.5 MHz, 5150-5600 MHz) are not only numerous, but also wide-ranging. Meanwhile, because the wireless repeater in the mine tunnel has great restrictions on the antenna size, the antenna has to be designed in a very small range of transverse size. In this paper, an ultra-narrow sized multi-frequency dipole (0.41λ × 0.04λ) is proposed to cover the optimal communication bands of underground mine tunnels with different cross-sections. This multibranch dipole consists of three main parts: lateral long branch, middle short branch, and end-loaded reverse branch. By adjusting the length of the two lateral long branches and utilizing the high harmonics, the antenna covers the lowest and highest operating bands that differ by a factor of seven. The middle short branch is one of the contributors to 1.4 GHz band. Meanwhile, the performance of the antenna at high frequencies is optimized by adjusting the distance between branches. The bandwidth of 1.4 GHz band is expanded by the loaded reverse branches. The test results are in good agreement with the simulation data, and the antenna covers all the optimal communication frequencies of underground mine tunnels with different cross-sections. Its peak gain at the resonance point is greater than 0 dBi, and the structure is simple.

To filter out the high harmonic content of the back electromotive force (EMF) in the conventional sliding mode observer (SMO), a novel flux SMO (FSMO) is designed in this paper. The feedback matrix is designed to replace the external filter or other modules, and its higher-order feedback characteristics further enhance the convergence of the FSMO. The Lyapunov function is used to assess the stability of the FSMO. Importantly, a compensated phase-locked loop (CPLL) with an angular compensation strategy is used to extract both position and speed information, resulting in less speed fluctuation and lower position estimation error. Furthermore, the simulation model and experimental platform are developed to evaluate the reliability of the proposed method. Both simulated and experimental results confirm that the proposed hybrid control algorithm performs well in both steady state and dynamic one, high or low speed of the system, with suppressed harmonics of 50.1% and 7.3%, respectively, and an improved response time of 54.1%, providing a concrete program for sensorless control of permanent magnet synchronous motors (PMSMs).

The time-varying amplitude error and phase error in the multi-channel will affect the system performance of Range Digital Beam Forming-Synthetic Aperture Radar (RDBF-SAR), which will lead to the elevation of the side lobes amplitude of the echo signal, thus affecting the quality of space-borne synthetic aperture radar (SAR) images. A multi-channel error compensation method for space-borne RDBF-SAR is proposed in this paper. The echo signals of each channel are aligned in the frequency domain. For the amplitude error, the amplitude error compensation factor is obtained by comparing the amplitude of each channel signal with the amplitude of the reference channel signal. For the phase error, the phase error compensation factor is obtained by conjugate multiplication of the phase of each channel signal and the phase of the reference channel signal. Reduce the amount of calculation by averaging. This method can well compensate the amplitude error and phase error, suppress the elevation of the echo side lobe, and make the synthetic aperture radar image more focused and accurate. Finally, the effectiveness of the method is verified by simulation experiments. Under the simulation conditions in this paper, the amplitude compensation reduces the side lobes pulse compression amplitude by 2~10 dB, and the phase compensation reduces it by -1~9 dB.

An innovative nonlinear (NL) modelling of K-band power amplifier (KPA) designed and fabricated in Gallium Nitride (GaN) technology operating at frequency f0=24 GHz is investigated in this paper. Two KPA prototypes are characterized by single- and double-frequency tests (SFT and DFT). Then, fitting memory NL model from SFT established for input-output power (Pin-Pout) characteristic @ f0 enables to the confirmation of KPA performance. Accordingly, the KPA presents 27.8 dB gain when Pin increases from -5 dBm to 20 dBm, 40.8 dBm saturation output power, and 38.6% saturation power added efficiency (PAE). Moreover, the DFT with f1=23.995 GHz and f2=24.005 GHz enables the assess to the third-order intermodulation distortion (IMD3) which is assessed from 10.4 dBc to 35 dBc. The KPA critical IMD3 is identified with the Pout variation range from 16.35 dBm to 36.35 dBm. The developed NL model is useful in the future for the electromagnetic interference prediction of multi-carried front-end transceiver communication system due to NL distortion signal.

This study presents a comparative analysis of Direct Torque Control with Space Vector Modulation (DTC-SVM) and Finite Control Set Model Predictive Control (FCS-MPC) applied to five-phase induction motors. Five-phase induction motors offer enhanced performance, reliability, and efficiency over traditional three-phase motors, making them suitable for high-reliability applications. The performance of DTC-SVM and FCS-MPC is evaluated through experimental implementation on a 3.5 kW five-phase induction motor, focusing on both dynamic response during speed reference changes and load variations, and static response, under steady-state conditions, as well as energy quality, specifically stator voltage and current. Experimental results show that FCS-MPC provides superior dynamic response, effectively managing speed changes and load variations, while DTC-SVM, owing to its fixed switching frequency, excels at reducing torque ripple and minimizing stator current harmonics. The choice between DTC-SVM and FCS-MPC depends on the application's needs, weighing dynamic performance, torque stability, and harmonic content. This study provides valuable insights for optimizing five-phase induction motor control and encourages future research to refine these methods or develop hybrid approaches that combine their strengths.

Synchronous reluctance motor (SynRM) has been a hot research topic in recent years. In this paper, a composite speed controller based on the concept of super-twisting sliding mode (STSM) control is designed and innovatively applied to SynRM. For current control, the maximum torque per ampere (MTPA) strategy is used. For torque control, a design method based on an STSM controller is given. In order to solve the chattering phenomenon existing in STSM, a simple structure disturbance observer (DOB) is further introduced as a feed-forward compensation to offset the disturbances. A novel composite sliding mode speed controller is formed based on DOB and STSM. By using Matlab/Simulink, a composite sliding mode speed control system was built. The characteristics of the motor such as current, speed, and torque were researched. Compared to the STSM controller, the speed overshoot of the new controller is reduced by up to 50% (for no-load start). The speed drop is reduced by up to 75% (for sudden load), and the recovery time is shortened by up to 50%. The results show that the designed composite speed control system has better dynamic performance.

This paper proposes a novel knowledge-based neural network approach that, in the absence of specific device SPICE models, can utilize the measured data of actual diode devices to map the existing diode coarse model to a more accurate package model through neural network mapping techniques, thereby achieving precise and efficient modeling of the small-signal characteristics of diode devices. A knowledge-based neural network model for packaged diodes is proposed, which enhances modeling accuracy by learning the discrepancies between the diode coarse model and the actual device data. A training method for rapid parameter adjustment is suggested, where the neural networks within the input and output packaging modules automatically learn and adjust, continuously optimizing their internal parameters to enhance modeling efficiency. Modeling experiments conducted on the measurement data of the MA4AGFCP910 diode show that the proposed packaged diode model can effectively and accurately match the small-signal characteristic data of the diode device.

This study presents a technique to enhance the bandwidth of substrate-integrated dielectric rod antennas. The technique involves adding a tapered grating at the antenna input, which improves impedance matching. The tapered grating converts some of the guided mode fields into leaky mode fields, leading to improved matching and broader bandwidth. The effectiveness of this approach is demonstrated through simulations and measurements, showing significant bandwidth enhancement in both X-band and Ku-band designs. The design parameters and optimization process are detailed, and the scalability of the technique is confirmed by its successful application to different frequency bands. A design for X-band demonstrates the effectiveness of this technique, yielding a bandwidth of 40%. Additionally, the technique is applied to a previously reported Ku-band design, resulting in an improved bandwidth of 52%, up from 36%. The paper concludes that the proposed tapered grating is an effective approach to enhance the bandwidth of substrate-integrated dielectric rod antennas, particularly for medium or high-gain applications.

The finite set model predictive control (FCS-MPC) method for quasi-Z-source inverter-permanent magnet synchronous motor (QZSI-PMSM) system suffers from the problems of unclear linkage between control objectives, complex control system, and poor control performance. A three-phase duty cycle modulation-based model predictive control (TDCM-MPC) strategy without cost function is proposed. In this strategy, the control objectives are converted firstly to make a connection between the control variables of inverter-side and motor-side, and based on it construct a system of nonhomogeneous linear equations to calculate the three-phase duty cycle. In addition, the three-phase duty cycles may have a secondary correction according to the size of the capacitor voltage error to realize the overall control of the four control variables. Finally, the driving pulse is generated based on space vector modulation (SVM) to obtain smaller steady-state ripples. The experimental results show that, compared with the conventional FCS-MPC, the proposed TDCM-MPC strategy reduces the computation of the control system and can obtain better control performance.

To address the issues of decreased electromagnetic torque, poor robustness, and failure of demagnetization fault detection caused by permanent magnet demagnetization and inductance mismatch in interior permanent magnet synchronous motor (IPMSM), a robust deadbeat fault-tolerant predictive current control (RDFTPCC) strategy based on cascade flux linkage observer (CFO) is proposed. The proposed CFO is constructed by combining a discrete model reference adaptive system (MRAS) with an improved non-singular fast terminal sliding mode observer (INFTSMO). MRAS and INFTSMO perform d-q axis inductance estimation and demagnetization fault detection, respectively. A better current prediction can be obtained via the parameter state information from CFO. Moreover, the RDFTPCC is constructed by the state information obtained from CFO, which can compensate for the torque deficit due to permanent magnet demagnetization and the control performance degradation due to parameter mismatch, hence realizing fault-tolerant control. The experimental results indicate that the proposed method exhibits stronger fault-tolerance and robustness than the conventional method when the IPMSM suffers from demagnetization fault and inductance mismatch.

To enhance the performance of microwave power transmission (MPT) systems' transmitting arrays, it is essential to comprehensively consider key factors such as beam collection efficiency (BCE), the level of sidelobes outside the reception area (CSL), and expense. Current transmitting array models commonly suffer from issues like low BCE, a large number of array elements, and complex feeding systems. Addressing these issues, this paper proposes a novel transmitting array design referred to as Large Spacing Nonuniform-Excitation Sparse Planar Array (LSNSPA) and introduces a new subarray partitioning algorithm named Multi-Parameter Dynamic Weight Particle Swarm Optimization for Rectangular Subarrays (MP-DWPSO-RS). The algorithm is capable of optimizing the subarray structure, as well as the element positions and excitations, during each iteration. This paper achieves a relatively higher BCE metric than other arrays by utilizing only a small number of sub-arrays, through the combination of a large-spacing distribution strategy and a sub-array partitioning strategy. Simulations have verified that the proposed MP-DWPSO-RS algorithm can achieve a BCE of nearly 94% when optimizing the LSNSPA with an aperture of 4.5λ × 4.5λ consisting of 8 × 8 elements.

This paper presents a super-wideband antenna for operation in X, Ku, K, Ka, V, and W band applications. A monopole antenna with a semi-circular shape, fed through a transmission line and a Co-Planar Waveguide (CPW), is presented. It has a bandwidth ranging from 11.5 GHz to more than 100 GHz. A Multiple-Input Multiple-Output (MIMO) system with quad elements is constructed from the proposed antenna. The MIMO elements are arranged in an orthogonal ar-rangement to decrease the coupling between them. The MIMO system performance is investigated. The antenna is fabricated and measured, and it has a maximum gain of 8.37 dBi. The maximum radiation efficiency of the proposed antenna reaches 95% over most of the band. For the MIMO system, the maximum Envelope Correlation Coefficient (ECC) is 0.06, and the Diversity Gain (DG) is 9.7 dB.

Subjected to external interference, the input current of a voltage source pulse width modulation (PWM) rectifier distorts, leading to fluctuation in the dc bus voltage. In order to suppress current distortion and DC voltage fluctuation caused by disturbance, a disturbance-resistant control strategy for the PWM rectifiers is proposed. The mathematical model of the conventional double closed-loop control system is built, and the disturbance compensation mechanism is investigated. In addition, the design procedure of the proportional-integral compensator (PIC) is provided. To validate the proposed method, simulation and experiment are considered. The results show that low input current distortion and high bus voltage stability can be realized using the proposed method under the condition of disturbance. The control method is simple and easy to implement in the practical application.

This paper introduces a multimode hybrid continuous class power amplifier utilizing a band-pass filter. It integrates resistive response amplifiers operating in three modes: class F, class J, and class F-1. Instead of the traditional quarter-wavelength line for harmonic control, an interdigital band-pass filter is utilized to manage harmonic impedance, enabling broadband operation, high efficiency, reduced circuit size, and improved out-of-band rejection. To demonstrate the approach, a multimode hybrid broadband high-efficiency power amplifier designed for 2 to 3.8 GHz range, achieving drain efficiency from 56.3% to 75.5%, saturated output power ranging from 39.1 to 41.2 dBm, and gain between 11.1 and 13.2 dB, is detailed and fabricated in this paper.

To enhance the reduction of radar cross section (RCS) and improve stealth performance, a phase cancellation and absorbing metasurface(PCAM)is designed in this paper. The PCAM is composed of a chessboard layout of circular units and square units, and it not only converts absorbed incident electromagnetic waves into heat to reduce the intensity of reflected electromagnetic waves, but also simultaneously controls the phase of the reflected electromagnetic waves, achieving phase cancellation. This enables the metasurface to be exhibited with ultralow backscatter. After simulation verification, the metasurface can achieve RCS reduction of over 15 dB in the 4.3-11 GHz range for vertical incidence, with a fractional bandwidth of approximately 87.6%, and over 15 dB in the 5.4-11.2 GHz range for a 30° oblique incidence, demonstrating good stability for oblique angles. The metasurface has increased the reduction level from over 10 dB to over 15 dB, significantly enhancing the RCS reduction. Additionally, in the co-planar state with a central curvature of 90°, it can also achieve RCS reduction of over 10 dB in the 3.2-9.9 GHz range, showing significant potential for practical applications.

Rebar corrosion is a common hidden danger in concrete structures, posing a serious threat to structural safety. Due to its concealed nature, detecting rebar corrosion remains a significant challenge. Recently, a new detecting principle for internal rebar corrosion: Magnetic Resonance Eddy Current Penetration Imaging (MREPI) is proposed. This method significantly enhances the detection depth of eddy currents through resonance amplification. In this work, the theoretical and numerical analysis of MREPI has been done. The results demonstrate the higher sensitivity than the traditional eddy current testing (ECT). Furthermore, we built an MREPI sensor by using nanocrystalline soft magnetic metal as magnetic core to detect the rebar corrosion. Experimental results show that the proposed sensor can effectively test rebar within concrete, with the imaging patterns of corroded rebar being distinguishable.