To tackle the slow response and insufficient interference resistance exhibited by permanent magnet synchronous motors (PMSMs) under traditional field-oriented control (FOC). This paper proposes an integral sliding mode controller (SMC) to improve the speed loop, and adaptive law is also developed using a nonlinear smooth function to eliminate the chattering phenomenon of the sliding mode control. Meanwhile, an extended state observer is designed to estimate and compensate for the disturbances caused by wind speed uncertainty and the system's internal disturbances. Then, model predictive control (MPC) is employed for the current loop to eliminate the overshoot and achieve fast tracking. Finally, a step-by-step model reference adaptive scheme (MRAS) is proposed to identify the parameters and eliminate the internal disturbances in addressing parameter perturbation in the motor during operation. The simulation results demonstrate that the enhanced system exhibits almost no overshoot, superior steady-state performance, quick dynamic response, and resistance to both internal and external disturbances, ultimately validating the efficacy of the approach.

Wireless power transfer (WPT) with dynamic charging capabilities is a promising technology that can charge moving objects in real-time. However, maintaining high-efficiency power transfer during vehicle movement continues to be a significant challenge. To address this challenge, this study proposes a dynamic WPT system that utilizes orthogonal transmitter and receiver coils, offering the advantages of stable output power and efficiency, even when the vehicle is in motion. Unlike other systems, the proposed topology eliminates the need for a complicated feedback control system, thereby reducing hardware costs. To verify the effectiveness of the proposed topology, a dynamic WPT system was implemented in this study. Measurement results demonstrate that even when the vehicle moves a distance of 400 mm (four times the length of the receiving coil), the output voltage and power variations are only 4.9% and 9.6%, respectively.

This paper presents an efficient algorithm to calculate the primary basis functions (PBFs) of the characteristic basis function method (CBFM) for the scattering from a dielectric object. The use of the Poggio-Miller-Chang-Harrington-Wu (PMCHW) integral equation discretized by the Galerkin method of moments (MoM) with Rao-Wilton-Glisson basis functions leads to solving a linear system. For a collection of incident waves and for a given block, the CBFM needs to invert the whole PMCHW self-impedance matrix to calculate the PBFs. By decomposing the PMCHW impedance matrix into four sub-matrices of halved sizes, related to the electric and magnetic surface currents and their coupling, the computation of the PBFs is accelerated by using the impedance matrix derived from the electric field integral equation (EFIE) combined with the physical optics (named POZ) approximation. In addition, the PO developed by Jakobus and Landstorfer [35], named POJ and valid for a perfectly-conducting scatterer, is extended to a dielectric surface. Recently, the MECA (modified equivalent current approximation, Li and Mittra [29]) based on the tangent plane or Kirchhoff approximation, has also been applied to expedite the PBF calculation. The presented method, HCBFM-POZ (H means halved), accelerated by the adaptive cross approximation (ACA), is tested and compared with CBFM-MECA and HCBFM-POJ on a cube and on a sphere. The numerical results show that HCBFM-POZ is valid for both the shapes, whereas the CBFM-MECA and HCBFM-POJ are not valid on a sphere.

Compelling evidence suggests that the interaction between electromagnetic metasurfaces and deep learning gives rise to the proliferation of intelligent metasurfaces in the past decade. In general, deep learning offers a transformative force to reform the design and working style of metasurfaces. A majority of the inverse-design literature announce that, given a user-defined input, the pre-trained deep learning models can quickly output the metasurface candidates with high fidelity. However, they largely ignore an important fact, that is, the practical input is always semi-known. In this work, we introduce a generation-elimination network that is robust to semi-known input and information pollution. The network is composed of a generative network to generate a number of possible answers and then a discriminative network to eliminate suboptimal answers. We benchmark the feasibility via two scenes, the on-demand metasurface design of the reflection spectra and the far-field pattern. In the microwave experiment, we fabricated and measured the reconfigurable metasurfaces to automatically meet the semi-known beam steering requirement that widely exist in wireless communication. Our work for the first time answers the question of how to cope with semi-known input, which is ubiquitous in a panoply of real-world applications, such as imaging, sensing, and communication across noisy environment.

Phased array radar (PAR) systems are critical for modern defense and surveillance applications, but their reliability and availability are affected by various factors, including physical and performance degradation. Furthermore, implementing prognostics and health management (PHM) framework for the whole radar system is challenging. To address these issues, this paper proposes an efficient solution by hierarchically implementing PHM frameworks in an active PAR (APAR) system. The proposed framework subsumes device-level, subsystem-level, and system-level health prediction models to enable comprehensive health monitoring and maintenance decision-making. This approach addresses the unique challenges involved in implementing PHM for the APAR system and facilitates the transition from traditional reactive maintenance practices to a predictive maintenance approach, thereby improving the overall system. Mathematical models that relate the radar's physical degradation to its performance deterioration are formulated, analyzed and presented. Subsequently, a Bayesian long short-term memory (BayesLSTM) architecture is developed and integrated into the proposed framework for estimating the remaining useful life (RUL) of critical devices/subsystems. The effectiveness of the proposed deep learning-based prognostic framework is evaluated through simulations and experimental studies. The proposed hierarchical framework has the potential to be applied to other radar systems that require effective health monitoring strategy.

The outage probability performance of a hybrid free space optical (FSO)/radio frequency (RF) system with a reconfigurable intelligent surface (RIS) assisted full-duplex relay is presented in this paper. The FSO link follows the Gamma-Gamma distribution over pointing error and atmospheric turbulence with random foggy impairments. The RF link between the relay and the destination is subject to Nakagami-m distributions, while the RIS links and the relay self-interference (SI) link follow Rayleigh fading. As a result, the RIS-to-relay link's cumulative distribution function (CDF) of the signal to interference plus noise ratio (SINR) is obtained. On the basis of this, the system's outage probability is determined according to the decode and forward relay protocol. Thus, Monte-Carlo simulations are utilized to verify the obtained expression's accuracy. Our findings show how atmospheric turbulence, pointing errors, fog conditions, and the number of RIS reflecting elements affect the system performance. Furthermore, it is concluded that, under the identical channel conditions, heterodyne detection performs better than intensity modulation/direct detection (IM/DD).

Wideband phased arrays for Electronic Warfare (EW) applications utilize narrowband phase shifters in a switched configuration to cover a multi-octave bandwidth in split bands. Wideband True Time Delay (TTD) line circuits are the best candidates to replace narrowband phase shifters in such systems, covering the complete operating bandwidth in a single step. The Transmit Receive Module (TRM) is a critical component of any phased array system. A novel design of a TTD line-based Octal Transmit Receive Module (OTRM) for a 32-element EW phased array over a frequency range of 1-6 GHz is presented in this paper. The OTRM is designed on a single multi-layer PCB by integrating eight transmit-receive (TR) channels, associated controllers, and power conditioning circuitry in a compact size and weight of 800 grams. The paper addresses challenges associated in design of TR channels to fit within the inter-element spacing of 14 mm and to achieve isolation of ≥40 dB between channels. The designed OTRM tunes time delay up to 508 ps maximum with a step of 2 ps by using a single TTD line circuit for ±45° scan coverage. The OTRM has demonstrated its potential capability for use in wideband Radar, EW, and Communication system applications. Efficient thermal management of the OTRM is achieved by introducing Copper coins below the final power amplifiers and a liquid cold plate to dissipate a heat load of 32 watts per TR channel. The proposed OTRM delivers transmit power of 8 watts (CW), receive gain of 25 dB, and a noise figure of 6 dB per TR channel with an overall efficiency of 19% (min) over a 5 GHz bandwidth. RF path analysis of the TR channel in transmit and receive paths is carried out using the Systemvue software tool. To verify the design of the OTRM over different time delay and attenuator states, measurements are conducted using a Vector Network Analyzer (VNA).

The fast inverse Laplace transform (FILT) proposed by Hosono is recently applied to various transient response problems in electromagnetics. The frequency-domain methods have been the mainstream of electromagnetic simulation for many years, and a lot of knowledge has been accumulated. The FILT makes it possible to utilize frequency-domain techniques to transient analyses, and it is expected to provide reliable transient response analyses. Since the evaluation points of the image function in the conventional FILT depend on the observation time, the scope of application is sometimes limited when evaluation of the image function takes a relatively long computation time. This paper modifies the FILT so that the evaluation points are independent of the observation time, and the number of image function evaluations is reduced.

The reliability of DC-bus capacitors in six-phase drives is an important issue in multi-phase drive systems, and the influence of symmetrical and asymmetrical motor winding loads on the lifetime of DC-bus capacitors is essential. This article uses the SVPWM modulation algorithm to analyze the current and voltage ripple of DC-bus capacitors in a six phase voltage source inverter. Then, by optimizing the capacitance value when searching for the maximum stress point, the capacitance range of DC-bus capacitors is determined. At a power factor of 0.6 and modulation ratios of 0.4, 0.7, and 0.9, considering the changes in ESR, current, and voltage ripple in the capacitor, taking 80% of the rated lifespan as an example, it is found that the lifespan of the DC-bus capacitors in symmetrical configuration of the motor winding is increased by 0.20%, 1.80%, and 10.08% compared to that in asymmetric configuration, respectively. Finally, the analytical and experimental results were compared with existing methods, and the experimental results verified the effectiveness of the proposed method.

Focused arrays are attracting increased interest because of their wide range of applications. Focusing the antenna's radiation in the near field requires proper phase distribution of the array elements that must be fed through many phase shifters. This work presents a design idea for a focused circular array antenna, whose focal distance can be varied by only a single variable phase shifter. The idea is implemented on a dual-ring circular array having a six-wavelength diameter and focused at five wavelengths by using a single fixed phase shifter. Theoretical analysis and computer simulations of a sample design using MATLAB and CST Microwave Studio show that a phase change of 0.9π leads to a four-wavelength change in the focal distance. A formula for the estimation of the depth of field DOF is derived. The proposed array offers a simple method to vary the focal length continuously by a single variable phase shifter. This idea can be utilized in hyperthermia, RFID, and imaging applications, where the position of the focal spot needs to be moved along the normal to the array.

Sepsis is a life-threatening infectious disease. Mitochondrial dysfunction is widespread in severe sepsis. The myocardium contains a large number of mitochondria, and the survival rate of sepsis decreases sharply when cardiac dysfunction is involved. Vericiguat (BAY 1021189) is a novel drug for the prevention of heart failure. In this study, we evaluated the mitochondrial function of septic mice and drug-treated mice by resonance Raman spectroscopy (RRS). RRS can accurately identify the Raman characteristic peak at 750 cm^-1, 1128 cm^-1 and 1585 cm^-1 attributed to the reduced cytochrome in septic mice. We found that the intensity of the characteristic peak was significantly decreased in septic mice, indicating an imbalance of mitochondrial redox function, while the function was improved in the drug-treated group. It proves that BAY has the potential as a novel treatment for mitochondrial dysfunction in sepsis.

A coaxially pin-fed multiband fractal square antenna is proposed in this paper. The designed antenna resonates in five bands: 5 GHz, 10 GHz, 13.2 GHz, 16 GHz, and 20.5 GHz. This multibands are achieved by using a fractal square antenna. The fractal square is formed from an initial square patch and then optimized with increasing fractal iterations to resonate at these bands. The fractal property of the design also helps in the miniaturisation of the antenna. The proposed antenna has gain ranging from 4.9 dB to 9.7 dB and radiation efficiencies from 70% to 98%. The proposed antenna is simulated using the CST microwave studio. The antenna is then fabricated, and its performance parameters are measured. After finding a match between simulated and measured results, the same antenna and its array are tested in a MATLAB simulation environment for direction of arrival (DOA) and adaptive beam forming (AB) at all five bands. Using different DOA and AB algorithms, the performance of the antenna array is evaluated. The ability to accurately estimate the DOA of all signals delivered to the adaptive array antenna allows it to maximise its performance in terms of recovering the required transmitted signal and suppressing any interference signal. Then, the beam of the antenna is modified using the DOA algorithm to generate a beam in the desired direction and nulls in the unwanted direction for proposed satellite communications.

In this research work, a low-profile microstrip patch antenna has been designed with broad circularly polarized resonant bandwidth. The designed antenna consists of an equilateral triangular-shaped radiating patch with two triangular coplanar parasitic elements along with a square-shaped ground plane. The unique feature of this antenna design is a generation of circularly polarized radiation by only optimum corner truncation of the two parasitic elements along with a small portion of the driver patch. The designed antenna can be used for (5.725-5.850 GHz) WLAN and (5.85-5.925 GHz) dedicated short-range communication applications with circularly polarized radiation property. The overall resonant bandwidth for (S₁₁ ≤ -10 dB) is 1.52 GHz 24.75% with a frequency range (5.38-6.90 GHz), and the circularly polarized resonant bandwidth for (Axial ratio ≤ 3 dB) is 240 MHz 4.13% with a frequency range (5.69-5.93 GHz). The gain of the antenna is 4 dB at 5.81 GHz and almost remains the same for the entire resonant bandwidth. The complete design of the antenna has been done using theoretical calculation and HFSS ver13 simulation software. After that, it has been fabricated, and different parameters have been measured using Vector Network Analyser. It has been found that the measured results are very much similar to the simulated results.

This study investigates beamforming and optimization in Multiple-Input-Multiple-Output Orthogonal-Frequency-Division-Multiplexing (MIMO OFDM) radar systems. The objective of this research is to mitigate the range-angle coupling effect in MIMO OFDM radar systems by adopting range compensation and distance-angle decoupling methods, which is to ensure that the signal processing during radar waveform formation does not impact the aforementioned coupling effect. In distance compensation, the CVX toolbox is used to minimize peak sidelobe after distance compensation is performed in the angle dimension. A mathematical model is established, and an optimal set of transmission frequencies is achieved through the use of the Alternating-Direction-Method-of-Multipliers (ADMM) algorithm in the context of distance-angle decoupling. Both methods effectively eliminate distance-angle coupling and enhance detection and identification capabilities of MIMO OFDM radar systems.

This research extends the theory of binomial array antennas. A closed-form expression for the half-power beamwidth of the array factor of an array antenna is presented. The expression is correct for the ratios of element spacing to wavelength greater than or equal to one quarter. Also, exact equations for determining the half-power beamwidth for main-beam steering are derived. A comparison with an approximate formula for the half-power beamwidth of binomial array antennas is carried out.

In the paper, a wideband circularly polarized (CP) filtering antenna is proposed, which is composed of four bent Vivaldi elements excited with sequential-rotated feeding technique. Since the Vivaldi element has the advantages of high gain and wide bandwidth, it is selected as the radiation element. On this basis, two cross slots are etched on the Vivaldi antenna to increase the gain at lower frequency band, and bent method which has less effect on the overall performance is applied for lowing the profile of the antenna. To realize filtering characteristic, the quadrature four-feed network consisting of one modified miniaturized filtering rat race coupler (FRC) and two compact wideband quadrature couplers is utilized as the sequential-rotated feeding for the Vivaldi elements. Design procedures of the Vivaldi antenna, the modified filtering FRC and the quadrature four-feed network are given. For validation, a prototype is fabricated and measured. Results show that more than 60% fractional bandwidth (FBW) is achieved under the criterions of more than 10 dB return loss and less than 3 dB axial ratio. Within the AR bandwidth, the gain is in the range of 7.5 dBic~10.1 dBic. Out of the operation band, the gain sharply decreases to be lower than -5 dBic with a rectangle coefficient (|Normalized Gain_-10-dB/Gain_0-dB|) of 1.25, which indicates good filtering performance.

A novel miniaturized high-gain Vivaldi antenna printed on a thin substrate is proposed for operation as multi-band antenna for millimeter-wave applications. The present work proposes a novel geometrical design of the Vivaldi antenna that is printed on the opposite faces of a thin dielectric substrate. The antenna has compact size, and its dimensions are optimized to enhance the performance regarding the bandwidth of impedance matching, gain, and radiation efficiency. To maximize the gain within a desired frequency band, each arm of the Vivaldi antenna is loaded by a ring-shaped parasitic element. The results of the parametric study for antenna design optimization regarding the enhancement of the impedance matching bandwidth and the antennas gain are presented and discussed. Also, it is shown through parametric study that the size and location of the parasitic rings can be optimized to enhance the antenna gain over the desired frequency range. The multiband operation of the proposed Vivaldi antenna is explained in view of the multimode operation that is illustrated by the distributions of the surface current on the antenna arms and the electric field in tapered slot. A novel microstrip line/parallel-strip line balun structure is proposed for feeding the balanced Vivaldi antenna and to achieve wideband impedance matching. The proposed Vivaldi antenna is fabricated and subjected to performance evaluation through measurements. It is shown that the antenna impedance is matched to 50 Ω over the four frequency bands: 22.0-27.7 GHz, 32.0-37.5 GHz, 41.5-46.6 GHz, and 51.7-56.7 GHz. The corresponding bandwidths are 5.7, 5.5, 5.1, and 5.0 GHz, respectively with percent bandwidths of 23%, 16%, 11.6%, and 9.2%, respectively. In spite of its compact size, the achieved values of the maximum gain are 6 dBi, 9 dBi, 11.4 dBi, and 12 dBi over the mentioned frequency bands, respectively. Also, the corresponding values of radiation efficiency are 98%, 97%, 95%, and 93%, respectively. The proposed Vivaldi antenna is fabricated and subjected to measurement for experimental investigation of its performance. The measurement shows good agreement with the simulation results.

A novel flexible printed monopole antenna with a windmill-shaped fractal design, which is fed by co-planar waveguide (CPW) is presented in this manuscript for ultra-wideband (UWB) applications. By integrating a modified windmill-shape fractal into the conventional irregular hexagonal-patch, the antenna achieves a significantly wider impedance bandwidth extending up to 156.6% across the frequency band of 1.37-11.25 GHz. Additionally, increasing the number of the windmill-shaped fractals leads to the emergence of further resonances. The overall dimensions of the designed antenna are 50 × 70 × 0.2 mm³, and it boasts an impressive bandwidth-dimension ratio (BDR) of 4457, showcasing exceptional efficiency in utilizing its compact size. The maximum gain reaches 4.8 dBi, while the radiation efficiency attains an impressive 98%. The modified windmill-shape fractal antenna design leverages the multifractal concept, providing monopole antennas with enhanced flexibility in controlling resonances and bandwidth. This manuscript offers a comprehensive presentation and discussion of the process used to improve the impedance bandwidth, shedding light on the antenna's exceptional performance and capabilities.

Circularly polarized gap-coupled designs of corner truncated square microstrip antenna in 2400 MHz frequency spectrum are presented. The gap-coupled design on thinner substrate (~0.036λ_g) yields axial ratio bandwidth of 113 MHz (4.697%) whereas that on thicker substrate (~0.13λ_g) yields axial ratio bandwidth of 471 MHz (19.24%). Both the designs exhibit broadside radiation pattern with a peak gain above 7 dBi, thus satisfying the requirements of WLAN and Bluetooth applications. Simulated results have been experimentally verified, which show close agreement.

In this paper, reactive impedance surface metasurface (RIS-MS) and negative refractive index metasurface (NRI-MS) are used to design a wideband, high gain, circularly polarized slot loaded patch antenna (SLPA) for 5 GHz WI-FI applications. The RIS-MS is utilized to improve the antenna's bandwidth. It is composed of 6×6 metallic circular patches that are periodic. To improve bandwidth, the RIS-MS is placed between the SLPA and ground plane of a conventional antenna. A metasurface lens composed of 6×6 periodic NRI metamaterial unit cells enhances the gain of the antenna. The NRI-MS superstrate is positioned at the optimal height above the conventional antenna. A prototype of the proposed antenna has been fabricated and measured experimentally. The prototype has an impedance bandwidth (IBW) of 21.7% (5.12-6.37 GHz), a 3-dB axial ratio bandwidth (ARBW) of 18.2% (5.19-6.23 GHz), and a gain of 13.5 dBic.