Reconfigurable antenna arrays play a major role in the current and future wireless communication systems due to their multifunctional capabilities and many other advantages. Conventionally, the array pattern reconfigurations were usually achieved by controlling the excitation amplitudes and phases of all or most of the array elements which are generally costly and complex methods. In this paper, a simple method for controlling the reconfigurability of beam-patterns of the linear and planar arrays is presented. It can be easily switched between narrow and wide beams using thinned-elements strategy. First, the array elements are divided into three groups based on their locations namely central, middle, and outer elements. Their amplitude weights are chosen to be unity, adaptive, and zero respectively. To add some desired constraints on the array beam-patterns such as limited sidelobe level and specified nulls placement, the excitation weights of the middle elements are optimized such that an abrupt change in the array taper is avoided. This also avoids an undesired change in the sidelobe pattern. A genetic algorithm is used to perform such optimization so that the produced beam-patterns are best matched to the desired ones. Moreover, the size of the thinned region controls the resulting beam width.

The problem of defeating a swarm of unmanned aerial vehicles (UAVs) is of considerable importance to the modern warfighter. In recent studies high power radio frequency (HPRF) directed energy weapons (DEWs) have been shown to be suitable for this purpose. Hence there is a need to develop mathematical modelling frameworks to quantify HPRF DEW performance, especially when they are operating in a wideband or ultrawideband mode. Consequently this paper introduces a novel mathematical model, based upon a new interpretation of UAV vulnerabilities to HPRF DEW, which permits performance assessment to be undertaken. The key to this is to view each UAV through its vulnerabilities to HPRF DEW energy at given frequencies and analyse its impact on the lifetime of each of the UAVs. This results in the definition of an appropriate stochastic process to count the number of UAVs still active in the swarm over a given time interval. Consequently this permits the determination of minimum HPRF DEW power levels at given frequencies in order to guarantee likelihood of defeat of the swarm before it reaches the HPRF DEW source. Hence the results in this paper will provide a novel framework for determining the specifications of an HPRF DEW's required power distribution over target vulnerabilities to ensure a desired level of system performance.

3D printing is revolutionizing manufacturing and is now being considered in the electronics industry. The creation of the first 3D volumetric circuit (3DVC) has created a way to make circuits smaller, lighter, into unconventional form factors and exploit physics like anisotropy more effectively than planar geometries can. While this is exciting, many problems mustbe solved to make 3DVCs a reality. One of these problems is electromagnetic interference and mutual coupling between components that are expected to be highly problematic in high-frequency 3DVCs. Spatially-variant anisotropic metamaterials (SVAMs) could be a solution to overcome this difficulty, but research in this area is not possible without a way to generate SVAMs around multiple components. In this paper, an algorithm is integrated into CAD software that can generate SVAMs for 3D circuits which will enable future studies of SVAMs.

In this paper, a low-profile miniaturized microstrip monopole antenna with an overall size of 15 mm × 20 mm × 1.6 mm is developed and analyzed for Ultra-Wide Band (UWB) services. The proposed antenna is carefully designed, optimized and analyzed using HFSS 15 simulation software. A prototype of the design is realized and experimentally tested as proof of concept. The results are discussed and compared with literature. They show attractive radiating features for UWB applications. The proposed antenna consists of an elliptical patch printed on a low-cost FR-4 epoxy substrate with a modified ground plane. To achieve UWB characteristics, elliptical rings are etched on the conducting patch, and the ground plane is modified by adding an inverted L shaped strip and creating a semi-elliptical slot in the partial ground opposite to the feed line. The achieved ultra-wide band ranges from 3.1 to 18.1 GHz (141.51%).

This article presents the design and implementation of a beam-steering antenna array using a 4x4 Butler matrix feed network (BMN) for 5G applications. The proposed antenna array can achieve a gain of 14 dBi and a steering range of (+16º, -47º, +46.5º, -15.7º) to cover angular range extending from 45º to 135º. To achieve that, a simple, 4x4 Butler matrix etched on a single-layer microstrip structure is designed, optimized, and fabricated. The proposed design incorporates phase shifters, 3-dB couplers, and cross-over couplers. The proposed matrix is employed as a feeding network for 4-element wideband LPDA antenna array. The fabrication results of the feeding matrix and antenna array show very good agreement with the simulated results.

Computation of the magnetic field generated by permanent magnets is essential in the design and optimization of a wide range of applications. However, the existing methods to calculate the magnetic field can be time-consuming or ungeneralised. In this research, a deep learning-based fast-computed and generalised model of three-dimensional (3D) magnetic field is studied. The volumetric deep neural network model (V-Net) which consists of a contracting part to learn the geometrical context and an expanding part to enable the concise localization was applied. We synthetically generated the ground truth datasets from permanent magnets of different 3D shapes to train the V-Net. The accuracy and efficiency of this deep learning model are validated. Predicting on 50 random samples, the V-Net took 4.6 s with a GPU T4 and 23.2 s with the CPU whereas the others took a few hundreds to thousands of seconds. Therefore, the deep learning model can be potentially utilised to replace the other methods in the computation and study of the magnetic field for the design and optimization of magnetic devices (the codes used in this research are published openly in https://github.com/vantainguyen/3D_V-Net_MagneticField).

This paper describes the design, fabrication, and test of a printed planar log-periodic dipole antenna to be used as a standard gain antenna in simple, low frequency, anechoic chamber far-field antenna measurements. The design procedure is size constrained by the photolithographic printing circuit fabrication process. Maximum gain and an input reflection coefficient below -10 dB are envisaged for the frequency range 0.5-2.5 GHz. The antenna is printed on a low cost FR4 substrate, and a careful analysis, with optimization of all the antenna physical parameters namely: number, length, spacing and width of the dipoles, width of the feed line traces, feed line termination, feed balun, and substrate shape, is carried out. The good agreement obtained between numerical simulation and experimental results provides validation of the proposed antenna configuration and design procedure.

This paper presents a miniaturized super wideband (SWB) antenna that has a high bandwidth dimension ratio (BDR). It is intended for use in microwave and millimeter-wave (mmWave) frequency applications. The designed antenna ensures low-dispersive behavior for both near- and far-field performance. The radiating element is composed of three circular rings that are interconnected by conical-shaped metal strips which lead to a fractal geometry. The design incorporates a partial ground plane and two parasitic patches located at the bottom and top sides of the substrate, respectively. The parasitic strips serve the purpose of enhancing impedance matching at lower frequency bands and reducing spurious radiation that may arise from the feed line. The proposed antenna has an overall size of 20×20 mm² and exhibits an impedance bandwidth (IBW) of ≈57 GHz, spanning from 2.86 to beyond 60 GHz with a fractional bandwidth (FBW) of 181.8%, a ratio bandwidth (RBW) of 21:1, and a BDR of 5036. Furthermore, the peak gain value is observed to be ≈11 dBi, while the average gain within the operating range is ≈6 dBi. The proposed antenna design was also fabricated and tested, and experimental results show a reasonable agreement with the simulated data. This makes the antenna extremely suitable for energy harvesting applications in future fifth-generation (5G) and sixth-generation (6G) networks.

A design method of compact dual-band multi-beam antennas is proposed by integrating a dual-band metasurface lens with a dual-band planar antenna array in this paper. The dual-band multi-beam antenna designed through this method has a compact configuration, low cost, and is easy to integrate with other devices for communication. The dual-band multi-beam function of the antenna by this method has been verified through a double-layer dual-band metasurface lens and a five-element dual-bandplanar antenna array. A dual-band meta-cell with relatively independent performance at 13 GHz and 23.5 GHz is designed to form the metasurface lens. Dual-band magnetoelectric (ME) dipole antenna is used as the feed antenna element. The simulated and tested results indicate that the lens antenna generates five independent beams at both 13 GHz and 23.5 GHz. Considering practical applications, solutions to improve antenna performance and reduce losses have also been proposed.

A new synthesis method of linear array antenna for wireless power transmission is introduced based on invasive weed algorithm in this paper. In order to improve the beam collection efficiency, the subarray division is carried out in the case of different azimuth angles and different numbers of array elements, respectively. Under the constraints of aperture size and minimum element spacing, the element positions, excitation coefficients and the element numbers of subarrays are optimized simultaneously. Compared with the optimization results obtained by other literature, it can be found that the proposed method in this paper can obtain a higher beam collection efficiency.

According to the characteristic mode basis function method (CMBFM) in analyzing electrically large problems, blocking and extending lead to the problem of slow convergence in the iterative solution of a reduced matrix equation, and the characteristic mode basis function method combined with principal component analysis (CMBFM-PCA) is proposed in this study. The characteristic modes (CMs), calculated from each extended block, are subjected to PCA to enhance the orthogonality between them and improve the reduced matrix's condition number to facilitate its quick convergence through an iterative solution. The corresponding numerical calculations demonstrate that significant efficiency and accuracy are achieved by the proposed method.

In this paper, a novel dual-band series-fed array (SFA) has been proposed. By introducing a new dual-band series-fed network (SFN) consisting of uniform transmission lines (TLs) and C-sections, independent beam direction can be realized. The design procedure for the proposed dual-band SFA has also been presented in this paper. To validate the design method, a prototype antenna has been fabricated and measured. The experimental results verify the performance of the proposed dual-band SFA.

This paper presents a stabilized scheme that solves the wave propagation problem in a general bianisotropic, stratified medium. The method utilizes the concept of propagators, i.e., the wave propagation operators that map the total tangential electric and magnetic fields from one plane in the slab to another. The scheme transforms the propagator approach into a scattering matrix form, where a spectral decomposition of the propagator enables separation of the exponentially growing and decaying terms in order to obtain a well-conditioned formulation. Multilayer structures can be handled in a stable manner using the dissipative property of the Redheffer star product for cascading scattering matrices. The reflection and transmission dyadics for a general bianisotropic medium with an isotropic half space on both sides of the slab are presented in a coordinate-independent dyadic notation, as well as the reflection dyadic for a bianisotropic slab with perfect electric conductor backing (PEC). Several numerical examples that illustrate the performance of the stabilized algorithm are presented.

A compact selective ultra-wideband bandpass filter primarily based on a multi-mode resonator is presented in this paper. A modified elliptical split-ring resonator (SRR) embedded in a variant of the ring resonator is employed to configure a microstrip ultra-wideband (UWB) triple-notched bandpass filter with improved in-band and out-of-band filter properties. Further, the bent inter-digital coupled lines with aperture at the backside are applied to overall filter size miniaturization apart from contributing tight coupling through the entire structure. The three notches facilitated by the modified elliptic SRR have gained the ability to suppress the wireless local area network (WLAN) (5.48 GHz), C band RADAR (7.68 GHz), X band RADAR (8.82 GHz) interfering signals profoundly within the UWB. Simultaneously, the other filter attributes likely a uniform forward transmission coefficient with minimum attenuation (0.46 dB~1.52 dB), a high skirt factor (0.88), a wide passband (6.52 GHz) with high fractional bandwidth (FBW) (103.16%), broad upper stopband (3.47 GHz), etc. together establish the proposed filter, suitable for practical UWB applications. The uniqueness of this design lies in the flexibility to configure the filter as either a double-notched or a triple-notched bandpass filter by altering only the aspect ratios of elliptical SRR. Simulated filter characteristics are compared with the results obtained by measuring the fabricated prototype, and a good accordance between the compared outcomes validates the design pertinence well.

A novel synthesis method of a sparse rectangular planar receiving array (SRPRA) to maximize the power transmission efficiency (PTE) for microwave power transmission (MPT) is proposed in this paper. The array element positions of the SRPRA are symmetrically distributed among different quadrants such that the array elements at symmetrical positions receive the same power, and the SRPRA adopts a sparse layout. This reduces the number of array elements and simplifies the complexity of the feeding network. An improved adaptive chaotic particle swarm optimization (IACPSO) algorithm is proposed for the optimization synthesis problem of the SRPRA. Through the optimization of the proposed IACPSO algorithm, the optimal element layout of the SRPRA can be obtained efficiently to get the maximum PTE. In addition, we conduct a series of simulation experiments to verify the advantages of the proposed SRPRA model and the effectiveness of the IACPSO algorithm. Firstly, we analyze the effects of different parameters on the synthesis results of the SRPRA. Secondly, comparing the results with those of the sparse random circular aperture array (SRCAA), it is demonstrated that the SRPRA synthesized with the IACPSO algorithm can obtain higher PTE with fewer elements and has a relatively simple feeding network. Finally, compared with the standard particle swarm optimization (SPSO) algorithm, the proposed IACPSO algorithm can effectively and stably obtain the synthesis results of the SRPRA under different parameters. Therefore, the SRPRA is suitable for creating an efficient MPT system.

In this article, a planar compact grounded coplanar waveguide (GCPW)-fed 4-element multiple-input multiple-output (MIMO) antenna array with a defected ground structure (DGS) is demonstrated for fifth generation (5G) millimeter-wave (mmWave) communication. Each element of GCPW-fed mmWave MIMO antenna array contains a deformed pentagon-shaped radiating patch etched with a pair of identical circular slots in top surface and a DGS in bottom surface. To maintain low design complexity and compactness, a DGS is introduced and formed by embedding dual asymmetrical inverted T-shaped slots in the partial ground plane which enhance the gain and bandwidth of the antenna. The equivalent circuit model of the proposed DGS loaded GCPW-fed antenna is realized and presented. The proposed 4-element mmWave MIMO antenna array is realized by arranging the 4 identical antenna elements horizontally in a row with a distinct gap without any decoupling structure. It has the size of 1.02λ × 3.86λ × 0.021λ (at 25.66 GHz) and exhibits the measured bandwidth of 49.62% (25.30-42.0 GHz) with a peak gain of 12.02 dBi. Furthermore, the envelope correlation coefficient (ECC) < 0.0014, isolation > 24 dB between antenna elements, and channel capacity loss (CCL) < 0.29 bits/sec/Hz of the mmWave MIMO antenna array are attained over the entire mmWave frequency band.

A highly packaged coupler using vertically placed inductors and capacitors (LC)-elements is proposed for 1 and 1.5 Tesla (T) magnetic resonance imaging (MRI) applications. The coupler is made on a 24-layer thickness low temperature co-fired ceramic (LTCC) substrate, and the full integration is reached by heaping up LC-elements in the vertical dimension. The coupler has a smallest reported size of only 0.0035 × 0.0021 × 0.001λg and a wide fractional bandwidth (FBW) of 44%. The measured in-band phase difference between the coupled and through ports and the amplitude imbalance are less than 91°±0.5° and 0.75 dB, respectively. Comparisons and discussions are also implemented.

Wide bandwidth compact rectangular and equilateral triangular microstrip antennas employing slots cut bow-tie shape ground plane profile are proposed. Amongst all the designs, patch employing three rectangular slots cut bow-tie shape ground plane yields optimum results. Using the rectangular patch, against conventional ground plane design, increase in bandwidth by 20%, resonance frequency, substrate thickness, and patch area reduction by 32%, 0.034λ_g, and 61.12%, are respectively achieved. In equilateral triangular patch design, a three rectangular slots cut bow-tie shape ground plane configuration shows bandwidth increase by 30%, and substrate thickness, fundamental mode frequency, and patch size reduction by 0.027λ_g, 16.4%, and 36.28%, respectively. Proposed designs exhibit broadside radiation pattern with broadside gain of above 5 dBi.

In this paper, we propose a wideband linear polarizer that utilizes metamaterial and metasurface techniques to achieve highly efficient polarization conversion. The proposed polarizer achieves a polarization conversion ratio exceeding 90% at 11.7-16.0 GHz, as confirmed by both simulated and experimental results. The effects of geometric parameters, incidence angle, and polarization angle on the performance of the polarizer are analyzed, and it is demonstrated that the polarizer maintains an extremely high polarization conversion efficiency even under wide-angle incidence. The polarization conversion mechanism is elucidated through the examination of eigenmode and surface current distribution. This work holds significant promise for the control of electromagnetic waves, making it essential for upcoming engineering applications.

This paper presents a coplanar waveguide (CPW)-fed tri-mode hybrid antenna that is suitable for quad-band applications. The antenna design is compact, measuring only 30×30 mm², and consists of a zeroth-order resonator (ZOR) antenna, a torch-shaped monopole antenna, and a T-shaped slot antenna. The most significant feature of this design is its ability to provide three independent working modes, making it a hybrid antenna. By incorporating a Composite Right/Left-Handed Transmission Line (CRLH-TL) unit cell, the first mode is excited as a ZOR antenna, corresponding to the lowest resonance at around 1.57 GHz. The second mode relies on the torch-shaped monopole antenna with two resonances at about 2.5 GHz and 3.5 GHz. The third mode employs the T-shaped slot antenna with a resonance at around 5.5 GHz. Experimental results demonstrate that the proposed antenna exhibits a wide and multi-band behavior with impedance bandwidths of 60 MHz (1.56-1.62 GHz), 210 MHz (2.30-2.51 GHz), 370 MHz (3.40-3.77 GHz), and 1100 MHz (5.05-6.15 GHz). This antenna can not only support the current GPS/WLAN/WiMAX systems but can also be considered as one element of a multiple-input-multiple-output (MIMO) antenna array for the fifth-generation (5G) mobile communication in the sub-6 GHz frequency range.