The present paper proposes a novel technique to reduce the peak side lobe ratio (PSLR) in the time waveform of the synthetic aperture radar (SAR) pulse. The dependence of the instantaneous frequency on the time over the SAR pulse duration is formulated as an arbitrarily shaped piecewise linear (PWL) curve. The slopes of the linear segments of this curve are optimized to get the minimum PSLR of the received radar echo at the output of the SAR receiver. The particle swarm optimization (PSO) method is used to optimize the shape of the time-frequency curve to achieve the dual-objective of minimizing the PSLR of the received SAR echo and to realize the required pulse compression ratio (PCR). The slopes of the linear segments of the time-frequency curve are the control parameters that determine the position of each particle in the swarm. The proposed method can be considered as an optimized form of non-linear frequency modulation (NLFM) for SAR pulse compression. It is known that the conventional NLFM using second-order time-frequency curve results in a PSLR of -18 dB. The proposed method results in a PSLR of -45.6 dB and achieves a range resolution of 1.4 m. The developed PSO algorithm is shown to be computationally efficient and its iterations are fastly convergent such that a few iterations are enough to arrive at the steady state of the cost function. Finally, a SAR transceiver is proposed as a software-defined radio (SDR) in which the proposed SAR pulse compression technique is employed in the transmitter to generate the transmitted pulse and in the receiver to construct the transfer function of the matched filter (MF).

This paper presents a forthcoming compact high-performance two-element multiple-input-multiple-output (MIMO) diverse antenna for wireless-LAN 5 GHz band and sub-6 GHz 5G(NR) band. The proposed antenna consists of two symmetrical antenna elements with an inverted T-shaped ground structure. The antenna attributes such as S-parameters, realized gain, current distribution, and radiation patterns are studied. Additionally, MIMO performance is also investigated in terms of envelope correlation coefficient (ECC), diversity gain (DG), total active reflection coefficient (TARC), and multiplexing efficiency. The antenna covers the entire 5G band for wireless communication, with an effective band (-10-dB) of 2.92 to 5.72 GHz (provides bandwidth of 2.8 GHz). The obtained values indicate that measured performance is in reasonable agreement with simulated one. Additionally, efficiency and gain were around 95 % and above 3 dB across the band of interest respectively.

In this paper, a low-profile triple-notched bandstop filter (BSF) is introduced. The proposed filter suppresses frequencies of Bluetooth (2.4 GHz), Wi-Max (3.5 GHz), and Wi-Fi (5.2 GHz) using three defected microstrip structures (DMSs). This BSF may be located in the feed line of an ultra-wideband (UWB) antenna. Consequently, not only the complexity is reduced, but also the area of the presented filter (24×10 mm²) is plummeted. Multiple rectangular slots are etched in the feed line to achieve multi-notch performance. Additionally, two dumbbell-shaped defected ground structures (DGSs) are etched in the ground plane to improve matching. Three PIN diodes are used to reconfigure the frequency response of the filter. By controlling the three diodes, the proposed filter can support six operating modes. The filter is simulated, optimized, fabricated, and measured to be suitable for cognitive radio applications. It achieves an insertion loss of (40, 29, and 24) dB and a rejection rate of (184, 215, and 277) dB/GHz at 2.4, 3.5, and 5.2 GHz, respectively. The simulated and measured results agree well.

This article introduces a new planar multiband antenna inspired by metamaterials. The design incorporates a split-ring resonator (SRR) on a printed monopole antenna for ultra-wideband (UWB) communication, generating a new resonant frequency within the Industrial, Scientific, and Medical (ISM) frequency band. The effect of SRR-inspired slots was examined using characteristic mode analysis (CMA), revealing that the placement of the SRR on the antenna's radiating structure created multiple resonant modes. To improve impedance matching, the ground plane of the antenna was modified. The antenna was fed using a 50 Ω microstrip line. The proposed antenna was simulated and fabricated on an inexpensive FR4 substrate with a thickness of 1.6 mm, a dielectric constant of 4.4, and dimensions of 38×40 mm². To validate the simulation results, the antenna parameters were measured. The results showed that the proposed antenna is capable of covering both the ISM frequency band (2.2-2.5 GHz) and the UWB frequency band (3-26 GHz). This makes it suitable for various wireless communication applications requiring UWB and ISM frequencies, offering a promising solution.

This article demonstrates the design development, fabrication, and testing of an off-set edge-fed monopole hybrid fractal antenna for ultra-wideband (UWB) applications at a design frequency of 3.2 GHz. The proposed monopole antenna is compact 38.12 mm × 38.42 mm, slotted, and uses a combination of two numbers of Koch plus Minkowski hybrid fractal technology. Antenna resonates at four frequencies i.e. quad tuned (3.2 GHz, 4.94 GHz, 7.21 GHz, and 10.10 GHz). The reflection coefficient, S₁₁ < -10 dB obtained for the excellent UWB fractional bandwidth 119.55% (2.85 GHz to 11.32 GHz) is more than the standard FCC bandwidth (3.1 GHz-10.6 GHz). The antenna has gained 6.73 dBi at 3.49 GHz, 5.91 dBi at 5.52 GHz, 8.26 dBi at 6.81 GHz, and 8.02 dBi at 10 GHz with a maximum radiation efficiency of 89.81%. The main feature of the proposed work is that the antenna is circularly polarized in frequency bands 3.14 GHz-3.30 GHz (Axial ratio: 1.61 dB) and 9.07 GHz-9.45 GHz (Axial ratio: 2 dB) and elsewhere linearly polarized. A total of 16.37% antenna size miniaturization has been achieved with excellent UWB and S₁₁ performance. The measured and simulated reflection coefficients are found in good agreement. Therefore the fabricated and tested antenna is well suitable for Wi-Max (3.3/3.5/5.5 GHz), ISM (5.725-5.875 GHz), WLAN (3.6/4.9/5.0/5.9 GHz), military band applications (radio location, fixed-satellite and mobile-satellite, S-band, C-band and X-band satellite communications, etc.), aeronautical radio navigation, radio astronomy, ITU-8, Sub-6 GHz band, and Radar applications.

This research article presents an innovative design of a textile-based microstrip patch antenna with a metasurface for medical applications. The antenna is designed to operate at a frequency of 2.4 GHz, which is the frequency of the Industrial, Scientific, and Medical (ISM) band, to minimize the Specific Absorption Rate (SAR) in the human body. The design includes an Electromagnetic Band Gap (EBG) that is placed above a metasurface, which is made up of a periodic array of I-shaped structures. A foam layer is placed between the EBG and the antenna to improve performance. The use of textile-based materials in the antenna allows for flexibility and comfort when it is mounted on the human body. The integration of the metasurface in the antenna design allows for a more efficient transfer of energy from the antenna to the surrounding tissue, resulting in a reduction in the amount of energy absorbed by the body. The simulation of the antenna design is carried out using Computer Simulation Technology (CST), which provides accurate results for the performance of the antenna. After the implementation of the EBG array, the gain of the antenna is improved, resulting in better performance. The proposed antenna design achieved a SAR value of 0.077 W/kg over 1 gram of thigh tissue, which is well below the safety limit set by the International Commission on Non-Ionizing Radiation Protection (ICNIRP). This implies that the integrated design of the antenna can be safely used inmedical applications.

This article presents the recent advancements in utilizing metamaterials for the development of high-performance antennas in 5G communications. The focus is on negative refractive index metamaterials composed of two unit cells: a complementary infinite split ring resonator (CI-SRR) and a Hilbert fractal embedded in the ground plane. These metamaterials enable antenna size reduction while enhancing performance. The proposed antenna metamaterials offer improved antenna characteristics and precise control over physical dimensions, facilitating the creation of highly efficient devices with miniaturized antennas. Additionally, an antenna array 1×3 is incorporated to further enhance performance. The antenna design has a compact size of 40×33×1.57 mm² and is fabricated using Rogers RT/Duroid 5880 material. The final broadband antenna exhibits a wide impedance bandwidth of 12.71% at 32 GHz, accompanied by a gain of 10.5 dBi. The comparison between wave concept iterative process (WCIP) calculations and measurements shows good agreement. The fabricated structure is thoroughly analyzed using a Keysight PNA network analyzer, demonstrating its successful operation and suitability for broadband applications.

In this paper, a pioneering and innovative approach for multiple-band ridge gap waveguide (MB-RGW) based narrowband bandpass filter for satellite applications is presented. The MB-RGW represents a significant and emerging technological advancement within the domain of microwave and millimeter-wave engineering. It comprises a periodic structure that enables the propagation of electromagnetic waves along its axis. We have provided a detailed analysis of the MB-RGW, which includes its design, simulation, and experimental results. A prototype filter, designed according to specifications, was successfully produced with a fabricated circuit area measuring 42.25 mm × 76.25 mm × 8.8 mm. We demonstrate that the MB-RGW can achieve multiple bands with a single structure, making it a versatile and efficient device for a wide range of applications. We also present a detailed analysis of the factors that affect the performance of the MB-RGW, including the geometry of the ridge and the spacing between ridges. Our experimental results show that the MB-RGW can achieve high levels of attenuation and isolation, making it a promising candidate for use in microwave and millimeter-wave circuits and systems. The experimental results show S₁₁ smaller than -20 dB over relative bandwidths, and S₂₁ has a maximum of -0.6 dB. The proposed filter demonstrates four resonances at frequencies of 10.6 GHz, 12.6 GHz, 14.7 GHz, and 17.1 GHz, catering to mobile and fixed radio locations as well as satellite applications. It exhibits a fractional bandwidth of 0.44% at 3 dB in the X-Band and approximately 0.57% to 0.61% at 3 dB bandwidth in the Ku-band. The filter offers a compact, cost-effective, and easily implementable solution for satellite communication systems, including space operations, earth exploration, satellite TV broadcasting, and fixed satellite services (FSS). Overall, this paper provides a comprehensive overview of the MB-RGW and its potential for the use in a range of applications.

An improved model-free nonsingular fast terminal sliding mode control (IMFNFTSMC) algorithm based on super-twisting extended sliding mode disturbance observer (STESMDO) is proposed to address the problems of control performance degradation and system failure of surface-mounted permanent magnet synchronous motor (SPMSM) under complex operating conditions. Firstly, the mathematical model of SPMSM under parameter ingestion is established; secondly, a novel hyperlocal model is proposed to combine with variable exponential approach law and the nonsingular fast terminal sliding mode (NFTSM) surface to design the speed-loop IMFNFTSM controller to accelerate the system convergence while reducing the sliding mode jitter. To enhance the control accuracy, the super-twisting extended sliding mode disturbance observer (STESMDO) is designed to estimate and feed-forward compensate the system disturbance. Finally, the effectiveness and superiority of the designed algorithms are demonstrated by comparing the proposed method with PI and the conventional model-free nonsingular fast terminal sliding mode control algorithm (MFNFTSMC) through simulations and RT-Lab experiments.

Currently, the inspection and verification of vehicle-related information are done by police inspectors using camera-based systems or manually. Though integrating video technology is more advantageous than manual operation, they do not perform accurately due to bad weather or driving styles. This paper presents the design of a compact, durable, battery-free, UHF RFID tag with enough memory to carry necessary information for automatic identification of traffic law enforcement applications. The vehicle owner can also be alerted when the tag is detected due to the visual indication facility. This tag's novel feature includes adapting a modified T-match structure to match the highly capacitive impedance of the chosen RFID sensor chip, i.e. Farsens Rocky100. In contrast to existing designs, the proposed tag contains no extra lumped components that necessitate an external impedance matching circuit. Instead, the input impedance was matched using an advanced T-match topology and by optimizing the antenna's geometrical features. Simulations were done in Ansys HFSS (High-Frequency Structure Simulator) whereas the dimensions of all the printed elements were fine-tuned using parametric optimization. The tag was fabricated on a low-cost FR4 substrate and measured. The tag with an overall size of 110 × 25 × 2.4 mm³ can be detected by a conventional UHF RFID reader within a range of about 0.2 m-1 m. Due to the loop configuration, the tag exhibits a confined detection range while operating well within short ranges.

Orbital angular momentum (OAM) is a fundamental characteristic of electromagnetic waves and has gained significant attention in recent years because of its potential applications in various fields of radio and optics. Furthermore, the OAM has been proposed as a means to increase the spectral efficiency of wireless communication systems. By encoding multiple independent data streams on different OAM modes of electromagnetic waves, OAM communication systems can increase the amount of information that can be transmitted over a single radio frequency channel. In this paper, we developed a new method for steering the OAM wave using an intelligent reflective surface (IRS) that is suitable for the far field. Specifically, we designed the IRS coefficients to reflect and steer different multiplexed orders between different users based on OAM waves by controlling the IRS impedance, which can be fluctuated depending on the beam steering direction. Moreover, we investigated the physical limitations of the IRS by noting the relations between the number of transmitted modes, the IRS size, and the impedance values in the IRS. Each impedance element in the IRS consists of real and imaginary values, and the negative values in the real part are used as an indication for reaching the physical limit. One suggestion to decrease the negative real values is by using windowing to decrease the beam waist. The proposed method may enable the extended coverage of OAM wireless communication.

A quad-element reconfigurable radiation pattern Multiple Input Multiple Output (MIMO) antenna is designed for WLAN and 5G applications suitable for indoor wireless communications. Antenna system consists of four radiating elements that operate over triband frequencies 2.4, 3.5 and 5.5 GHz. Moreover, the pattern diversity is obtained by introducing two diagonally crossed slots in the radiator to steer the main beams of the antenna in eight different angular directions using eight PIN diodes. The overall physical dimension of the proposed antenna is about 0.55λ₀ × 0.55λ₀. In addition, an Acrylonitrile Butadiene Styrene (ABS) enclosure is designed, and the performance of the proposed antenna is evaluated. The measurement results show that the proposed antenna has an impedance bandwidth of 4.18%, 14.13%, and 28.5% at the said frequencies, respectively.

This work examines the effects of high frequency radio transmission on the human body. A magnetic point source is used to generate a signal that is transmitted through the human body at a specified distance. The study was conducted to evaluate the health effects of exposure to high frequency radiation, in relation to current density, induced electric field and specific absorption rate at frequencies of 6.78 MHz and 13.56 MHz. The results for both an equivalent cylinder and a realistic human body model were compared. The analytical method presumes a sinusoidal current distribution along the cylinder and introduces the approximations of field integrals. The numerical simulations by the commercial software FEKO confirmed the analytical results depicted in the paper. The study shows that maximum differences between the results of the proposed analytical model and human model (regardless being realistic or cylinder) are less than 10%. This is convenient because analytical methods can ensure fast estimations of the exposure standard limitations.

In recent years, the non-embedded uncertainty analysis method has been widely used in the field of Electromagnetic Compatibility due to its wide application range. In this paper, from the perspective of the practical application of uncertainty analysis methods, four non-embedded uncertainty analysis methods are applied to the worst-case estimation of Electromagnetic Compatibility, which are the Monte Carlo Method, Stochastic Collocation Method, Stochastic Reduced-Order Models, and Kriging surrogate model method. The performances of four uncertainty analysis methods in terms of computational accuracy, computational efficiency, and ability to deal with complex problems are compared in detail by using the parallel cable crosstalk prediction example in the existing literature and the uncertainty analysis example of self-constructed optimization test function, which provides a theoretical basis for uncertainty analysis method to guide the actual Electromagnetic Compatibility design.

A hybrid-fed dual-polarized antenna with matesurface coverage is proposed in this paper, which can be used for 5G mobile communication base station antennas. By placing the two feeding ports on different layers of dielectric plates in an orthogonal manner, and using electromagnetic coupling and slit coupling for feeding respectively, the antenna can achieve inter-port isolation higher than 35 dB in the operating frequency band. In order to widen the bandwidth and obtain higher gain, the metasurface covering unit is loaded above the patch. The metasurface layer contains an array of 5 × 5 square patch units printed on the top surface of the dielectric plate. The measurement results show that the proposed antenna has an impedance bandwidth of 12% (3.24 to 3.66 GHz). In addition, the antenna obtains a stable gain of about 5.32 dBi at 3.5 GHz. The proposed antenna meets all the requirements of base station antennas and can be a promising candidate for application in 5G base station systems.

Parallel computing for the three-dimensional spatial spectral volume integral equation method is presented for the computation of electromagnetic scattering by finite dielectric scatterers in a layered medium. The first part exploits the Gabor-frame expansion to compute the Gabor coefficients of scatterers in a parellel manner. The second part concerns the decomposition and restructuring of the matrix-vector product of this spatial spectral volume integral equation into (partially) independent components to enable parallel computing. Both capitalize on the hardware to reduce the computation time by shared-memory parallelism. Numerical experiments in the form of solving electrically large scattering problems, namely volumes up to 1300 cubic wavelengths, in combination with a large number of finite scatterers show a significant reduction in wall-clock time owing to parallel computing, while maintaining accuracy.

This study describes a noncontact low-cost X-band sensor system for determining the soluble solid content (SSC) of a sugar solution. The system adopts a transmission signal technique with two frequency pairs (10.2 GHz paired with 10.4 GHz and 10.2 GHz paired with 10.6 GHz) from three transceiver modules. Each module has a microstrip patch antenna, mixer circuit, and dielectric resonator oscillator. To simplify the transmission power frequency of each frequency pair, the frequency is down-converted to an intermediate frequency (IF) signal using a frequency mixer. The IF signals are then compared using a gain and phase detector to find their magnitude ratio and phase difference. The measured SSC-level data are randomly divided into three datasets and input to an artificial neural network (ANN) for training. The training output is the SSC level in Brix degree. The proposed ANN structure comprises four input nodes, eight hidden nodes, and four output nodes, affording low complexity and resource savings while providing 92.98% accuracy. Therefore, the proposed low-cost sensor system can achieve precise decision-making and real-time measurement.

Doubly Salient Singly Excited Machine (DSSEM) inbuilt with the features as high torque density, high speed density, compactness, low maintenance, but the machine reduces its application due to its demerits as torque ripple. This study enhances the performance of switched reluctance motor (SRM) in the track of electromagnetic and mechanical characteristics. A 290 Volts, 10 Amps, 3000 rpm, 4 N-m SRM undergoes finite element (FE) characterization in the view of parameters like torque ripple. In the regard of torque characterization, the ripple torque is estimated under rated condition. FE analysis gives accurate results by 2D analysis. Torque ripple is the main concern in electrical machines, because these two are responsible for producing harmonics, vibration, and noise. So, a novel machine is designed to reduce the torque ripple content. The losses are considered as heat generation as a source of temperature rise in a motor, and the heat distribution is analyzed. The experimental setup is arranged to evaluate the simulation results with the current profile of FE analysis and prototype for verification.

This paper presents a multiband flexible wideband coplanar waveguide (CPW) wearable slot antenna for biomedical and Internet of Things (IoT) applications. The proposed antenna comprises an elliptical patch with a slot designed on top of a thin and flexible polyimide substrate of thickness 0.1 mm. CPW feeding with slotting on the ground and a protruding microstrip from the ground on one side of the patch is used to have resonance at multi-frequencies for the proposed antenna design. The measured results show that the developed antenna resonates at 2.81 GHz with an impedance bandwidth of 0.8 GHz (2.23-3.2 GHz) and at 4.43 GHz, 5.96 GHz, and 9.38 GHz with an impedance bandwidth of 6.7 GHz (3.5-10.3 GHz). The proposed antenna is simple and portable to mount on any part of the human body and obtains justified specific absorption rate (SAR) values. The prototype of the suggested antenna underwent the fabrication process. A comparison of the antenna parameters was carried out, and there was a reasonable correlation between the simulation and measured results. The proposed antenna is a good contender for Wireless Body Area Networks (WBANs) and IoT applications.

Owing to the principle of relativity, the present state of knowledge explicitly allows Maxwell's equations to be solved not only in the rest frame of an electromagnetic transmitter but also directly in the rest frame of the receiver without use of the Lorentz transformation and the Lorentz force. Recently, such a calculation was first performed for the Hertzian dipole. The analysis of the resulting formula breaks new scientific ground and indicates that Maxwell's equations predict that electromagnetic waves in vacuum propagate at the speed of light, notably for each receiver, even when these receivers have relative velocities with respect to each other. Although this paradoxical phenomenon was expected, the finding that Maxwell's equations nevertheless predict a classical Doppler effect was unexpected and indicates inconsistent or not yet fully understood aspects of canonical Lorentz-Einstein electrodynamics consisting of Maxwell's equations, Lorentz force and Lorentz transformation.