High frequency electromagnetic plane wave scattering by a large rectangular glass window on a conducting wall has been analyzed in this study. Scattering far-fields are formulated by means of the Kirchhoff approximation in which the fields are obtained from radiation integrals due to the equivalent current sources on the virtually closed window apertures. In order to consider the effect of the window glass, a dielectric slab layer has been inserted in the window hole, and the reflection and transmission through the slab are treated via waveguide modal theory. The validity of our formulation has been confirmed by the numerical comparison with another method for an empty window case. The effects of the window dimension, the glass layer, and the polarization have been discussed for practical high frequency mobile communications.

The present work proposes a novel cow-head shaped multiple input multiple output (MIMO) antenna for 5G sub: 6 GHz applications, which include N77/N78 (3.3-4.2 GHz/3.3-3.8 GHz) and N79 (4.4-5.0 GHz) bands. The proposed work is designed and developed on a 30 × 66 mm² size FR4 substrate with a dielectric constant of 4.4 and loss of tangent of 0.002. The proposed design works in the region from 3.3 to 5 GHz, and an isolation above 18 dB is attained. The parametric analysis and surface current distribution are studied for the optimization of parameters, and the coupling between elements is analysed respectively. The performance of design is studied in terms of efficiency (≥ 91.5 %), peak gain (3.1-4.6 dBi) and radiation patterns (E & H fields). The diversity parameters (ECC, DG, TARC, CCL & MEG) are calculated and checked, the same as measured results. Then all the measured results of fabricated prototype is compared with simulated ones, and these are in good agreement.

Low-Radar Cross Section antennas attract substantial attention in Stealth Technology. The Radar Cross Section reduction performance of the microstrip antennas should be improved since they contribute to the overall Radar Cross Section. A novel microstrip patch antenna with a polarization converter metasurface is proposed to extend the Radar Cross Section (RCS) reduction bandwidth. The metasurface uses metallic strip structures to obtain the required polarization conversion for Radar Cross Section reduction. The proposed patch antenna shows the overall RCS reduction bandwidth of 7.25 GHz-24.83 GHz (110%) as compared to the metal sheet and the Reference Patch antenna. 10 dB RCS reduction is obtained from 8.33 GHz-9.16 GHz (9.49%) and from 12.81 GHz-18.85 GHz (38.16%) as compared with the Reference Patch antenna. The RCS reduction of the antenna and the antenna radiation patterns are verified by numerical simulations and experimental observations. The main novelty of the proposed design is its wideband RCS reduction for Transverse Electric as well as Transverse Magnetic polarization with enhancement in antenna radiation pattern parameters. Significant RCS reduction can also be obtained for oblique incidence.

This present article reports a high isolation four-port Wrench shaped compact UWB MIMO antenna with a novel decoupling network in the ground plane, and its step-by-step evolution is presented for 3.1-10.6 GHz. The proposed four-port MIMO antenna is fabricated on an FR4 substrate of size 44×44 mm² (0.342λ₀ × 0.342λ₀), where λ₀ is a free space wavelength at 2.33 GHz, with 7\,mm edge-to-edge spacing between the radiating elements. It consists of four orthogonal symmetrically placed identical radiating elements each of which has a Wrench-shaped circular patch with a rectangular slot cut in the partial ground. The performance characteristics of this MIMO antenna are reflection coefficients S₁₁ ≤ -10 dB in the range from 2.33 GHz to 11.7 GHz, mutual coupling coefficients S₂₁ ≤ -28.24 dB, and S₃₁ ≤ -22.35 dB. The maximum peak gain is 5.15 dBi at 9.2 GHz, minimum is 1.27 dBi at 3.1 GHz. The maximum peak gain is 5.15\,dBi at 9.2 GHz, and minimum is 1.27 dBi at 3.1 GHz. The maximum efficiency is 98% at 4.66 GHz, and the minimum is 93% at 6 GHz. The diversity parameters of proposed four-port MIMO antenna are reported as ECC ≤ 0.2, DG ≤ 10, TARC ≤ -10 dB, the ratio of MEG between any two elements is near unity, and CCL < 0.38 bits/s/Hz in the band of interest. The design is fabricated and measured. The measured and simulated results are in good agreement and are within the permissible limits.

This paper presents the design and practical implementation of a wideband spring textile (WST) antenna for wearable communications. The antenna is designed on a felt substrate having a compact dimension of 32 × 42 × 3 mm³ (0.38λ_g × 0.5λ_g × 0.036λ_g). This antenna operates in the 3.14 to 5.45 GHz frequency range, has a bandwidth (BW) of around 2306 MHz, and has a peak realized gain of 6 dBi at 3.5 GHz. Due to a broad frequency coverage, this antenna can be used in a wide range of wireless applications, including 5G and IoT. The proposed design is analyzed in terms of reflection coefficient, radiation pattern, efficiency, gain, and surface current. Using the same electromagnetic simulation software, both characteristic mode analysis (CMA) and the method of moments (MoM) are applied in the design process. The simulated results on a human chest phantom demonstrate the -10-dB impedance bandwidths of 1461 MHz. The antenna prototype is fabricated for verification, and the simulated and measured results demonstrate that the proposed antenna is suitable for wideband on-body applications given its low-profile implementation and mechanical flexibility.

This article presents the design of the dipole antenna structure in combination with a square electromagnetic band gap (EBG), to detect child trapped in carsuse the 750 MHz frequency range, which responds to the most human movement detection. The antenna structure has been designed on a copper plate with a thickness of 0.297 mm and polyester mylar film. The baseplate has a thickness of 0.3 mm, dielectric value 3.2. By design, the dipole antenna is the size as 201.56x12.5 mm² and a 18x5 units square Electromagnetic Band Gap (EBG) is the size as 254.64x71.86 mm². The results of the measurement showed that the bandwidth impedance in the operating frequency range was 4.78% (735-771 MHz) with a gain of 6.33 dBi, and has an omnidirectional signal. The dipole antenna has the best distance between the EBG plates 30 mm. When being examined at a distance of 500-1,600 mm, it is the most effective at an average signal strength of approximately 0.032 mW in every time there is movement of the human in the car.

In this paper, a new fast and accurate method, the Flux Integral Path (FIP) method, is proposed for switched reluctance motor (SRM) to analyze the iron loss. The magnetic flux generated by the stator poles is integrated over a period of time, then, the eddy current loss and the hysteresis loss of the whole SRM can be directly calculated by analyzing the path distribution of the flux closed loop without dividing the motor into four blocks (stator pole, stator yoke, rotor pole and rotor yoke). The concept of flux flow is introduced to calculate the eddy current loss, and the piecewise linear fitting of flux density curve in the period is used to approximate the differential and simplify the hysteresis loss calculation. The FIP method can be well applied to non-sinusoidal and nonlinear magnetic density of SRM because of the combination of Finite Element Analysis (FEA) simulation. Furthermore, the loss separation model and the Fast Fourier Transform (FFT) method were compared with the FIP method of the iron loss calculation, and the 2D FEA simulation results were used to verify the method proposed in this paper.

Caves are a vital environment with an understudied propagation characteristic to date. In this paper, we investigate the propagation environments of three tourist caves in Malaysia at 900 MHz, 2.4 and 5.8 GHz. Path loss exponents are derived from measurement data for line-of-sight (LoS) and non-line-of-sight (NLoS) sections for vertical-vertical (VV) and horizontal-horizontal (HH) polarizations. Channel fading effects are subsequently analyzed. Beyond the conventional method of computing the path loss exponent values, machine learning is also incorporated into the processing of data for yielding optimum results. The findings of this work lay a good foundation towards a greater understanding of the propagation scenarios in natural tourist caves, and they help towards establishing reliable wireless communications inside such environments.

Metamaterial absorbers are widely used in sensing, cloaking, imaging, etc. Currently, most metamaterial absorbers are integrated with hard substrates, which limit their applications for non-planar and irregularsurfaces. In this paper, a flexible, foldable metamaterial absorber is proposed using a matrix-assisted catalytic printing method. The absorber is composed of periodically patterned eight-round sector copper arrays supported by a polyethylene terephthalate substrate. Experimental results show that the absorber exhibits one absorption peak near 10.2 GHz.

In this article, a metamaterial-inspired decagon-shaped antenna was designed with the dimensions of 30 x 30 x 1.6 mm³ for the vehicular applications that fall under GPS (Global Positioning System), LTE (Long-Term Evolution), UMTS (Universal Mobile Telecommunication System), WLAN (Wireless Local Area Network), Wi-Fi (Wireless Fidelity), INSAT (Indian National Satellite), etc. Initially, a conventional decagon-shaped monopole antenna was designed for the frequency of 4.5 GHz. Then, a decagon-shaped metamaterial unit cell was designed for the frequencies of 1.5 GHz, 2.4 GHz, and 3.5 GHz which were inspired on the monopole antenna to obtain the desired passbandcharacteristics under vehicular bands. All the simulations were done in the ANSYS High-Frequency Structure Simulator (HFSS) 2019 R2 version. In order to determine the metamaterial characteristics of the proposed unit cell, Scattering Parameter Retrieval Method has been used, and the values of permeability have been obtained through MATLAB. Further to examine the antenna performance in vehicular communication, it is placed on the rooftop and front side of the car model in simulation and on a physical car. Return loss characteristics were observed in the simulation as well as in the open space measurement, and the radiation pattern is analyzed with the SBR+ (Shooting and Bouncing Rays) method. The gain and radiation efficiency of the antenna get increased when it is mounted on the car model which is beneficial for the proposed application.

In this paper A capacitive coupled Dielectric Resonator Antenna (DRA) array with log periodic method is explored experimentally for X-band applications. The incidence free DRA series consists of seven rectangular Dielectric Resonators (DRs). For both DRA and MPA arrays, a series fed microstrip line was used. In this work, Log Periodic Microstrip Patch Antenna (LPMPA) and Log Periodic Dielectric Resonator Antenna (LPDRA) arrays have been designed and realized, and the performance characteristics such as return loss, VSWR, gain, and bandwidth are simulated and validated experimentally. The LPMPA antenna is in active state from 10.2 GHz to 12.9 GHz with a bandwidth of 2.7 GHz and a gain of 8.55 dB. The LPDRA antenna is in active state from 7.3589 GHz to 12.1060 GHz with an increased bandwidth of 4.7474 GHz and a gain value of 8. 53 dB. The corresponding performance characteristics are presented at the end.

A new formulation for the finite-difference time-domain (FDTD) technique is presented, for nonlinear circuit components provided that their X-Parameter representations are known. Transient electric fields at specified locations within the FDTD simulation are updated based on the frequency domain behavior of a multi-port nonlinear device, using the X-Parameter behavioral model. The formulation is demonstrated through the simulation of a nonlinear common-emitter amplifier embedded in a microstrip circuit with X-Parameters calculated from SPICE simulation results. Agreement may be seen between the X-Parameter-based simulation results and those acquired using a lumped-element method.

In this article, an open T-shaped stub resonator-based compact microstrip low-pass filter (LPF) with low in-band insertion loss and wide attenuation band is proposed. The folded T-shaped stubs loaded with T-shaped open stubs are symmetrically embedded in the high impedance line of the microstrip structure. The proposed LPF operates at a cut-off frequency of 2.4 GHz, a roll-off factor (ROF) of 62 dB/GHz resonated up to -48.5 dB at the resonant frequency, and an insertion loss of 0.35 dB in the passband region. In the ground plane of the LPF, two dissimilar defected ground structures (DGS) are placed in the array to generate additional attenuation poles for enriching the performance of the stopband. The sixth harmonic suppression is achieved up to 14.6 GHz and relative stopband rejection of 144%. The EM simulated results show a well-matched behavior with the experimental ones. The proposed LPF can be used for Bluetooth, Wi-Fi (2400 MHz), and microwave oven (2450 MHz) applications.

A planar, handheld device size compatible, multiple-input multiple-output (MIMO) antenna design is proposed. The antenna system has five antennas which cover multiple wireless bands. One pair of elements covers the frequencies below 1 GHz (559 MHz to 828 MHz) for Long term evolution (LTE) and Cognitive radio (CR) applications and frequency bands 1.68 GHz to 1.77 GHz, 2.48 GHz to 2.63 GHz, 3.3 GHz to 3.4 GHz, and 5.79 GHz to 6 GHz for Internet of Things (IoT). The other pair is a modified truncated tetrahedron wideband antenna which covers multiple bands like 854 MHz to 958 MHz, 1.38 GHz to 1.56 GHz, 1.75 GHz to 1.87 GHz, 2.08 GHz to 2.49 GHz, 3.29 GHz to 3.47 GHz and 4.09 GHz to 6 GHz including the triple radio frequency identification (RFID) bands. The antenna is designed and simulated using CST microwave studio simulator and antenna prototype is fabricated to obtain the experimental results.

The performance of the Capon beamforming sharply decreases against strong directional and large deviation interference. In order to reduce the impact of the abnormal interference, this paper proposes a large degree of freedom null broadening beamforming for non-circular signals. The signal vector is first extended by a uniform linear conjugate array. The covariance matrix of the array is then reconstructed by projection transformation and diagonal loading technique. Finally, the beamforming is constrained by the characteristic subspace of the guide vector matrix, and the analytic expression of the optimal weights of the method is derived. The numerical simulations demonstrate that the proposed null broadening method has the advantages of high degrees of freedom and strong parameter selection robustness.

A frequency multiplexed coding metasurface controlling beam is proposed to enrich the functions of a single metasurface. A square F4B dielectric substrate with a copper-clad bottom surface and a V-shaped and quadrangular cross-shaped metal structure is used as the unit. Applying the different responses of x and y polarized waves and optimization of structural parameters, we can obtain 1-bit coding units for the two frequency bands. The reflection phase can be modulated independently of each other. The design of a dual-band metasurface with different beam splitting effects was realized, achieving the goal of different frequency multiplexing functions on a single metasurface. An RCS reduction of 11 dB at 12 GHz and a double beam splitting at 20 GHz with a pitch angle of ±47.6° are achieved by metasurface. The test results agree well with the simulation results. The proposed metasurfaces offer a simple structure, low cost, good performance, and promising great applications in areas such as frequency multiplexed communications.

An efficient 0.6-4.2 GHz GaN-HEMT power amplifier based on Klopfenstein taper is proposed in this letter. A method based on source-pull/load-pull simulation has been used to find the optimum source and load impedances across the broad band. Then the Klopfenstein taper is studied and adopted for the output matching circuit design to achieve broadband performance. The measured results show that our proposed power amplifier has a fractional bandwidth of 150%, with saturated output power ranging from 39.45 to 42.32 dBm, power added efficiency from 45.1% to 64.8%, and over 9 dB gain at the whole working band of 0.6-4.2 GHz. The fabricated power amplifier can cover most of the wireless communication frequency bands.

An ultra compact antenna for low frequency application is presented. The resonant frequency band of the proposed antenna is centered at 403.5 MHz, employed for medical implant communication service (MICS) band. The proposed antenna is designed and fabricated on a substrate with ε_r = 4.4, tanδ=0.02 and thickness h = 1.6 mm. The size of the antenna is only 0.04λ₀ x 0.022λ₀ x 0.002λ₀ (29 mm x 16.5 mm x 1.6 mm), making it very compact for low frequency of operation. The antenna is evolved from a CPW transmission line. During the process of evolution of the proposed antenna, dual-composite right left handed (D-CRLH) behavior is confirmed from the dispersion diagram. The equivalent lumped circuit model for the antenna is also developed, and the D-CRLH behavior is also confirmed from the circuit model.

In this paper, a novel compact high-gain multi-layer dielectric resonator antenna for ultra-wideband applications is designed and fabricated. The proposed antenna employs a new technique to make a notch-band for the frequencies within UWB. This technique helps avoid any interference for bands like WLAN and X-band for satellite applications. In this design, several notch bands can get at different frequencies by changing the length of slots. The operating bandwidth of this antenna is between 4.8 GHz and 11.31 GHz with -10 dB return-loss and maximum gain of 6 dBi. Finally, the proposed antenna is fabricated and measured to validate the simulation results. The simulation results are obtained by two different simulators; CST Studio suite TM 2020 and HFSS 15 to ensure the validity of the design results before fabrication. The fabricated antenna is measuredusing Agilent R&S Z67 VNA. There is a good agreement between the simulation and experimental results.

A high-precision and high-efficiency reduced-dimension direction of arrival (DOA) estimation algorithm based on an L-shaped array for the problems of large computation and high cost of achieving two-dimensional (2D) DOA estimation by 2D multiple signal classification (MUSIC) algorithm under various complex arrays. The algorithm makes full use of the structural characteristics of the L-shaped array to decompose the uniform L-shaped array into two uniform linear arrays. These two arrays are respectively searched in one-dimension (1D) to estimate the angles between the source and the x-axis and y-axis, and then the 2D DOA estimation is obtained according to the geometric relationship, which greatly reduces the amount of computation. Furthermore, the algorithm increases the utilization of noise subspace information, which not only realizes the automatic pairing of direction angle and elevation angle, but also improves the estimation accuracy. In order to further reduce the complexity and improve the estimation performance, this paper also puts forward the root finding method instead of 1D search, and uses a fast angle matching method to accurately match angles. Simulation results show the feasibility of the proposed algorithm.