The paper represents a rigorous solution to the problem of diffraction of a normally incident plane electromagnetic wave by a circular hole in a perfectly conducting screen of arbitrary thickness, obtained using the eigenmode technique with allowance for the presence of a plane dielectric layer on a thick substrate behind the screen, which can play a part of a radiation detector. The main goal of the work is to describe the effect of diffractionlensless focusing in circular apertures and to determine the conditions of its appearance in the near zone of small holes, when its radius, the thickness of a screen and a dielectric layer are of the order of the wavelength.

In emergency departments and ICUs, a novel noncontact thermometer is urgently required to measure physical temperatures through common clothing to accomplish body temperature precise measurement for critical patients. Hence, a Ku band digital auto gain compensative microwave radiometer is proposed to get a higher theoretical temperature measurement sensitivity than a Dicke radiometer, benefit miniaturization design and reduce attenuation caused by common clothing. Meanwhile, a novel compensation method for receiver calibration is proposed to improve temperature sensitivity under non-ideal conditions, and the revised systematic calibration method is elaborated. Furthermore, in order to invert body physical temperatures through clothing, a microwave thermal radiation transmission model of clothed human body is constructed, and the microwave radiation apparent temperature equation of clothed human body is derived. Importantly, three groups of experiments are set up to confirm the designed radiometer's performance, especially the biological tissue temperature measurement. Results show that: 1) the designed radiometer has high temperature sensitivity and accuracy for unsheltered targets; 2) amplitude attenuation caused by cotton cloth for Ku band microwave is much smaller than that for infrared thermal radiation; 3) the designed radiometer can track physical temperatures of targets (such as water and swine skin tissue) sheltered or covered by cotton cloth relatively accurately. In conclusion, our designed Ku band microwave radiometer is certificated to have outstanding performance in temperature measurement for biological tissue through common clothing, which can be developed into a promising product in medical monitoring.

In this paper, an ultra-miniaturized, planar dual-band wearable antenna is proposed for bio-telemetry applications. The proposed antenna covers the 433 MHz and 915 MHz Industrial, Scientific, and Medical (ISM) bands with a compact volume of 0.000000384λ₀³. The antenna consists of a meander line on the top side of the substrate, while the backside is loaded with an inductive grid structure to achieve miniaturization. Moreover, the absence of vias in the design of the antenna offers a significant benefit in terms of simplifying the fabrication process. The design approach considers the integration of other components for device-level architecture. The antenna exhibits stable performance when placed on different human body parts, such as the head and hand. The evaluated specific absorption rate (SAR) complies with the regulated human safety standard. Additionally, the link margin (LM) calculation shows that the antenna could establish a biotelemetry communication link at a distance of 20 meters.

In order to remove the influence of the aperture fill time (AFT) for wideband array, the scaling principle of the Keystone (KT) transform is applied to eliminate the linear coupling between spatial domain and frequency domain of wideband array signal. However, the classic KT transform is implemented by interpolation Sinc which is difficult to apply in engineering and leads to the serious problem of insufficient data. To address this, a realization of the low-complexity KT transform is presented, and it is implemented using only the Chirp-z transform (CZT) and fast Fourier transforms (FFT). Additionally, an Autoregressive (AR) model is proposed to compensate the insufficient data for each range, and the order of AR is estimated by the rank of the signal covariance matrix. Simulation results demonstrate that the proposed algorithm significantly reduces computational burden and improves the performance of wideband array beamforming.

This paper presents a novel gap coupled suspended multiband microstrip antenna suitable for wireless applications like long term evolution (LTE), wireless local area network (WLAN), Amateur radio, and Sub 6 GHz 5G wireless applications. The proposed antenna is a single layer geometry suspended in air that employs a gap-coupled feed with a parasitic strip for tuning the input impedance. The overall dimensions of the antenna are 41.4 mm x 39 mm x 3.12 mm. The presented antenna offers a total of six resonant frequencies centered at 1.70 GHz, 2.77 GHz, 3.03 GHz, 4.26 GHz, 4.58 GHz, and 5.64 GHz. Measured resonant frequencies fairly match the simulated values. Further, the gain values at these frequencies are 7.29 dBi, 6.10 dBi, 7.39 dBi, 5.39 dBi, 6.22 dBi, & 7.03 dBi, and the corresponding measured gain values are 6.92 dBi, 7.72 dBi, 4.88 dBi, 5.34 dBi, 4.25 dBi, and 6.51 dBi, respectively. Radiation patterns were measured at all these frequencies and found to have highly stable radiation characteristics except for slight asymmetry at the high frequency end of the operational band.

Composite materials are being widely used in the automotive industry where they are progressively replacing metallic materials as structural parts for being robust and lightweight. Their complexity, often leading to lots of unknown behavioral effects when placed near the electronic systems present in vehicles, should be studied and treated. In the automotive industry, the shielding effectiveness of these materials should be considered as the most important parameter to be known in advance. Faurecia, one of the world's largest leading automotive suppliers, sought to assess the shielding effectiveness of their product such as dashboards and door trims. Their objective was to enhance the shielding effectiveness, thereby ensuring superior isolation and protection of electronic systems against electromagnetic interferences (EMI). Thus, this paper presents a novel method for characterizing the shielding effectiveness of various composites using two electromagnetic methods to cover a wide frequency range, starting from 10 Hz up to 8 GHz. The first method, based on loop antennas, was used to cover the low frequency range starting from 10 Hz up to 120 MHz. Frequencies between 100 KHz and 1.5 GHz were not discussed in this paper because of the many studies that already exist at this frequency range, using the coaxial transmission cell. The second method used for frequencies higher than 1.5 GHz, consists of ultra-wide band antennas (Vivaldi).

A new non-singular fast terminal Sensor-less sliding mode control algorithm (INFTSMC) for IPMSM based on an improved extended sliding mode disturbance observer (IESMDO) is constructed to address the problem of degraded control performance of IPMSM because of uncertainties. Firstly, a mathematical model of IPMSM under parametric ingestion is developed, and a new control law for the speed loop is designed. Then, an improved non-singular fast terminal sliding mode speed controller (INFTSMC) based on a novel extended sliding mode disturbance observer (IESMDO) is designed, where an improved super-twisting control law is designed to speed up convergence, while IESMDO can accurately observe the unknown perturbed part F of the system in real-time relative to the sliding mode disturbance observer (SMO). Finally, high-order square root cubature Kalman-filter (CKF) combined with an adaptive estimator is proposed to accurately estimate the speed and rotor position of the motor in real-time. Through simulations and semi-physical experiments with PI and traditional NFTSMC, it is verified that the algorithm has better transient steady-state performance when external disturbances and parameter perturbation are added externally to the motor, which is conducive to improve the control effect of IPMSM.

Today's 5G wireless communication evolution system demands millimeter wave frequency range antenna for its uses in several applications for future communication devices. A 2-port Asymmetric Flare-Shape Patch Multiple Input Multiple Output (MIMO) antenna for mm-wave communication system is designed and presented. The antenna structure is constructed on a Rogers RT Duroid 5880 dielectric substrate with 1.6 mm thickness, 2.2 dielectric constant, and 0.0009 loss tangent. The constructed MIMO structure has an overall size of 14×19.2 mm². The proposed MIMO design has -10 dB return loss performance over a frequency range of 20-40 GHz with more than 20 dB isolation between antenna elements, which shows the low mutual coupling between antenna elements. The performance of the suggested MIMO antenna is reported in terms of return loss, gain, ECC, surface current, and radiation pattern. The simulated and measured MIMO antenna performance characteristics are in good agreement. The suggested design achieves more than 20 dB isolation and 8.17 dB gain with an ECC value lower than 0.0002, which meets the diversity performance of the MIMO design with two antenna elements. The proposed MIMO design is compact and the best choice for 5G mm-wave applications.

Over the last three decades, the presence of electromagnetic radiation in the open environment has increased by many folds due to wide utilization of cellular data and voice communication over multiple wireless communication bands. Thus with the increased utilization of electromagnetic energy, several global as well as national electromagnetic exposure regulatory norms have been put in effect across geographical boundaries to safeguard humans from immediate effects of Radio Frequency radiation. Specific Absorption Rate (SAR) quantification is well established in literature to measure the rate of electromagnetic energy absorption by living objects (humans as well as plants) while external microwaves impinge on them. It should also be considered that plants do absorb fairly reasonable amount of electromagnetic energy mainly from cell tower and Wi-Fi antennas owing to high permittivity (ε'_r) and conductivity (σ) of constituent tissues. However, it is indeed unfortunate that worldwide there are very limited concerns regarding electromagnetic energy absorptions in plants, fruits and flowers - thus, no electromagnetic exposure regulatory guidelines have yet been put in effect to safeguard plants, crops, fruits and flowers. Thus, it is absolutely necessary to quantify microwave energy absorption rates in various fruit, flower and plant models due to electromagnetic radiations from different sources. Later on, consequent biological responses in plants along with associated effects on ecosystem and fruit nutrition value should be investigated. With this motivation, electromagnetic energy absorption rates i.e. SAR values along with associated spatial distributions have been estimated in this article for a typical Peace Lily (Spathiphyllum wallisii) plant model considering different frequencies of exposure, directions of plane wave incidence and polarizations of incident wave. Peace Lily plant has been chosen for this investigation as it is known for air purifying capability and indoor usage - furthermore, the plant parts can easily be characterized and modelled for electromagnetic simulations. Plants are of asymmetric shapes with varied sizes. To represent the typical geometric shape considering the most practical observation, a three dimensional Peace Lily plant model has been designed using CST Microwave Studio electromagnetic solver. The model has been exposed to linearly polarized plane waves at three distinct frequencies (947.50 MHz, 1842.50 MHz and 2450 MHz) following Indian electromagnetic exposure regulatory guidelines - these frequencies are used for voice, data or Wi-Fi communications. Dielectric properties (ε_r) i.e. permittivity (ε'_r) as well as loss tangent (tanδ) of different peace lily plant tissues have been characterized over a broad frequency band employing open ended coaxial probe measurement technique. Measured tissue dielectric properties (ε_r) have been fitted to the developed plant model to evaluate SAR data and spatial distributions. At each frequency, significant variations have been noted in magnitudes and positions of Maximum Local Point SAR (MLP SAR), 1 g averaged SAR and 10 g averaged SAR values for six different combinations of direction of arrival and incident wave polarization. Observations indicate different orders of change in MLP SAR, 1 g averaged SAR and 10 g averaged SAR values in the plant model even for same combination of frequency of exposure, power density, direction of arrival (plane wave) and polarization of incident wave. Data reported in this article can be considered as reference to investigate consequent physiological or molecular responses in plants and revise electromagnetic exposure regulatory policies to protect plants and the entire ecosystem.

This paper proposes a dual notches ultra-wideband (UWB) bandpass filter (BPF) with high selectivity and wide stopband. It is composed ofa novel multi-mode resonator (MMR) known as a double-T-shaped open stub-loaded MMR, a pair of interdigital coupled lines, and folded split ring resonator. The MMR is designed to place the resulting resonant modes within the UWB passband, then add interdigital coupled lines to achieve strong coupling, resulting in a flat passband. Afterward, multiple complimentary folded split ring resonators (CFSRRs) and folded split ring resonators (FSRRs) are embedded into the designed basic UWB filter to develop dual notches at the desired frequency. The filter is simulated and manufactured using low-cost high-frequency dielectric substrate F4BM. The measurement results agree well with the simulation data. Multiple notches centered on 5.8 and 8 GHz effectively suppress unwanted signals from 5.8 GHz WLAN and 8 GHz satellite systems simultaneously. In addition, two transmission zeros on both sides of the passband are located at 2.7 GHz and 10.76 GHz, respectively, so that the sharp skirt selectivity is improved to 0.857. The measured filter can exhibit high sharp selectivity and wider stopband at the same time.

In view of the problems of excessive magnetic flux leakage of the traditional permanent magnet fault-tolerant vernier rim-driven motor, low utilization rate of permanent magnets and high price of permanent magnet materials, this paper proposes a flux-concentrating consequent-pole permanent magnet fault-tolerant vernier rim-driven motor structure. Firstly, combined with the magnetic field modulation theory, the no-load air gap magnetic density of the motor is analyzed, and the working principle of the multi-harmonic operation of the motor is explained according to the harmonic analysis. Secondly, parametric modeling is used to screen the critical structural parameters that can significantly affect electromagnetic performance of the motor, and the response surface method and sensitivity analysis are used to rank the sensitivity of the critical parameters. Then, the high-sensitivity parameters are first subjected to multi-objective optimization, and then adjusted according to the low-sensitivity parameters. Finally, the air gap magnetic density, back- EMF, cogging torque and permanent magnet numbers of the motor before and after optimization are compared and analyzed by finite element analysis. The results show that the flux-concentrating consequent-pole permanent magnet vernier rim-driven motor has higher torque density, less torque ripple and higher utilization of permanent magnets.

In this paper, a compact, symmetric, simple, and highly selective Ultra Broad Band (UBB) Band Pass Filter (BPF) is constructed on a low-loss Taconic dielectric substrate. The top layer of the BPF is loaded with three headphone-shaped Defected Microstrip Structures (DMSs) and four Open Circuit (OC) stubs whereas the bottom layer is etched with three star-shaped Defected Ground Structures (DGSs). The proposed BPF is designed and simulated using High-Frequency Structure Simulator (HFSS) software at f₀. The proposed BPF shows 20 dB return loss and 0.4 dB insertion loss in the 3 dB passband covering 0.52 GHz to 17.1 GHz owing to 16.58 GHz Band Width (BW). Additionally, 10 dB and 25 dB upper stopband rejection is achieved with 1.3 GHz and 1 GHz BW respectively. Maximum group delay of the simulated filter is about 2.95 ns. The fabricated model transmits from 0.8 GHz to 17.4 GHz which in turn offers a 16.6 GHz BW at 3 dB level. The reflection coefficient of the fabricated filter is about -18 dB, and insertion loss varies from 0 dB to 0.72 dB inside the Transmission Band (TB) with a Fractional Band Width (FBW) of 178.5% and 3.35 ns maximum group delay. Moreover, the occurrence of Transmission Zeroes (TZs) and Reflection Poles (RPs) make the filter highly selective and low-loss (flatness). The measured results agree with the simulated outputs with slight deviations due to fabrication tolerances and connector loss. The size of the filter is 0.36λ_g * 0.36λ_g. Thus proposed filter is suitable for mobile phones, and satellite communication applications approximately covering L, S, C, X, and Ku frequency bands.

A systematic technique for switching between horizontal and vertical polarizations is introduced. A fan-beam antenna array for base station applications employing a grounded reflector is implemented, and the proposed approach is implemented and validated on it. The antenna array is realized using planar monopole elementary elements against a non-parasitic reflector, which yields a desirable fan-beam pattern. The corresponding 3 dB H-plane beamwidth can be easily adjusted by changing the reflector height. Two versions of the antenna arrays are used to demonstrate suppression of unwanted asymmetrical modes in the current distribution yielding improved cross-polar isolation. The measured H-plane 3-dB beamwidth is approximately 127 degrees at 900 MHz and 124 degrees at 955 MHz. The corresponding side lobe level is almost -11.7 dB and -8.7 dB at 900 MHz, while the back lobe level of -9.3 dB and -11 dB at 955 MHz from measurements. The gain is within the acceptable level in both cases and compared with simulations that possess good agreement. By taking into account the antenna design and manufacturing aspects, such antennas will pave the way to be employed in OFDM reconfigurable antenna applications and Identification Friend or Foe (IFF).

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.