This letter proposes a miniature bow-tie antenna element and its 2 × 2 arrays based on ball grid array (BGA) packaging technology for 5G millimeter-wave new radio (NR) applications. The antenna substrate uses ultra-economical single-layer FR4 printed circuit boards (PCB) to reduce manufacturing costs. By adopting solder balls, the antenna achieves the BGA packaging and realizes the surface mounting function. One bow-tie patch is excited by a plated through-hole (PTH) connected to the feeding point. The other bow-tie patch is directly short connected to the ground plane by another PTH. Besides, the bottom ground plane can be equivalent to a reflector, allowing the antenna element and array to obtain broadside radiation. For ease of integration, the input impedance of the antenna is set to 50 Ω. The measurement results show that the -10 dB bandwidth of the antenna element is 21% covering 25.2 to 31.1 GHz. The measured peak gains of the antenna element and the 2 × 2 arrays are 7.6 and 10.75 dBi, respectively. The proposed antenna element and array cover N257 (26.5-29.5 GHz) and N261 (27.5-28.35 GHz) bands. It is very suitable for the 5G millimeter-wave application.

A 37-43 GHz endfire antenna based on ball grid array (BGA) packaging is proposed for the fifth-generation (5G) wireless system. The antenna consists of a miniaturized radiator and reflector. Besides, the radiator is fed by a substrate integrated waveguide (SIW). Furthermore, the RF transition from the SIW to grounded coplanar waveguide (GCPW) and vertical quasi-coaxial is realized on the substrate. The antenna is implemented on a single-layer substrate using standard printed circuit board (PCB) technology to reduce costs. Then, the cost-effective antenna element is reflow soldered with solder balls to form a BGA packaging. The advantages of the BGA packaging and the three-dimensional (3D) integration are discussed in detail. The miniature packaging achieves a compact size of 7 mm × 3.4 mm × 0.6 mm. Finally, a prototype was manufactured to verify the performance. The measurement results show that the proposed antenna is a good candidate for 5G millimeter-wave (mmWave) New Radio (NR) applications.

The letter presents a compact, cost-effective, and surface-mount patch antenna element for 5G millimeter-wave (mmWave) system integration. The antenna element adopts ball grid array (BGA) packaging technology to achieve surface mount function, which can be applied to highly integrated systems. By adding a ring slot on the radiating patch, the proposed antenna obtains a wider impedance bandwidth. The antenna prototype has been simulated, manufactured, and verified. The proposed antenna element size is 5 mm × 5 mm × 1.3 mm. The measurement results show that the proposed antenna element can be used in the N257 (26.5 to 29.5 GHz) and N261 (27.5-28.35 GHz) frequency bands.

The resonant frequency will be changed, and the load voltage will be unstable with misalignments and load variations in wireless power transfer (WPT) systems. In this paper, the expression for solving the resonant frequency is obtained. The calculation result shows that the resonant frequency is changed with the changes of misalignment and load. First, a new control method of frequency tracking with a Fuzzy proportional-integral (PI) compound controller is proposed, which can eliminate the overshoot of resonant frequency and improve the speed of frequency tracking. Second, a mixed-modulation method for adjusting frequency and voltage is further proposed, which is mainly composed of the selection algorithm of the duty cycle, the phase-shifting angle calculation, and the method of frequency tracking based on the Fuzzy PI compound controller. The appropriate duty cycle is obtained by the selection algorithm of the duty cycle to adjust the load voltage. The phase-shifting angles of different duty cycles are obtained by the phase-shifting angle calculation, which play a role in adjusting the resonant frequency by combining the Fuzzy PI compound controller. The proposed method can not only make the system keep a resonant state, but also make the output voltage across the load stable. A WPT system via magnetically coupled resonance is designed. Calculation and simulation results validating the superiority of the proposed method are given.

In this paper, we derived Analytical Kirchhoff Solutions (AKS) for bistatic scattering near the specular directions at P band and L band for applications in Signals of Opportunity (SoOp). The land surface profiles are divided into three scales: microwave roughness f₁, fine scale topography f₂, and coarse scale 30-meter DEM f₃. The microwave roughness and the fine scale topography are treated as random rough surfaces, while the coarse scale topography from DEM data are treated as deterministic planar patches. The salient features of the AKS model are (i) analytical expressions are obtained for both coherent waves and incoherent waves, (ii) Monte Carlo simulations are not required making the AKS computationally efficient, (iii) the analytical solutions are expressed in terms of the spectrum, so that the dividing line between microwave roughness and fine scale topography is not required, and the rough surface spectrum derived from lidar elevation measurements can be incorporated directly. The results of the three approaches, AKS, the Numerical Kirchhoff Approach (NKA) and the Fine Scale Partial Coherent Patch (FPCP) model, are indistinguishable for both the coherent waves and the incoherent waves. The agreements validate the AKS and FPCP approaches as NKA is a brute force accurate method based on Kirchhoff integral using 2 cm discretization and high-performance computers. Results show that the f₂ profiles of fine scale topography have significant effects. The results of three Kirchhoff approaches fall in-between the results of the two versions of Geometric Optics (GO) approximations to the Kirchhoff integral [1, 2]. The two GO versions are with and without attenuation due to microwave roughness. The GO with microwave attenuation is also known as the ``Improved Geometric Optics Model (IGOM)''. Numerical results of coherent waves and incoherent waves are illustrated for remote sensing of snow and soil moisture at P band and L band. For P band, the histograms of the phase are shown. Results of the coherent waves are dependent on the sizes of the area as well as topographical elevations and slopes. AKS results are used to illustrate the coherent waves at P band on area sizes up to 1.5 km using 30-meter DEM topography elevations and derived slopes at Sanford, Brazos Peak, and Lobato Tank, Colorado, USA. For L band, the AKS results of Cross-Track are in good agreement with CYGNSS data over San Luis Valley, USA. In comparing CPU, it takes merely 25 seconds on a single CPU core for AKS to compute for a 15 km by 15 km DDM pixel which has 250000 DEM 30-meter patches. The CPU for AKS is slightly more than the 20 seconds required for GO.

A MIMO antenna with ACS- asymmetric coplanar strip feeding technique with compact size for UWB applications of band-notched features is presented. The proposed MIMO antenna contains two orthogonally placed rectangular-shaped radiating elements. The orthogonal mechanism of placement of radiating elements provides a good amount of isolation from 3.09 GHz to 11.13 GHz. The size of the antenna is 27 × 27 mm². The isolation is more than 17 dB for most of the UWB range. The proposed MIMO antenna represents nearly omnidirectional radiation pattern and low value of envelope correlation coefficient. Because of the usage of ACS feeding techniques, the antenna size is reduced, and it is a uniplanar structure. The diversity performance of the MIMO antenna is explained in terms of ECC-Envelope Correlation Coefficient, DG-Diversity Gain, and TARC-Total Active Reflection coefficient.

RAdio Detection And Ranging (RADAR) is an essential tool used extensively to detect a target's presence within the vicinity characterized by the range of the RADAR. In order to localize the target, Direction of Departure (DOD) and Direction of Arrival (DOA) estimations are utilized. To make it more convenient, a bistatic multiple input multiple output (MIMO) configuration is exploited to deduce the position of a target through the triangulation method easily. Furthermore, due to the maneuvering of targets in space, more robust direction finding solutions can be derived using Time-Frequency (TF) representations. Thus, this paper aims to leverage the benefits of TF analysis for the estimation of DOD and DOA jointly for a bistatic MIMO radar. The performance of the considered method is numerically evaluated and is compared against the conventional algorithms that do not use TF tools and as well compared against the Cramer Rao Lower Bound (CRLB). The results show that TF based approach may be a promising candidate in terms of its robustness against channel noise. Also, the performance of the TF based DOD-DOA estimates is studied in terms of their consistency and resolvability of targets which measures the performance in a multi-target environment. Finally, the use-case of TF based estimation to solve the problem in the presence of coherent targets is analysed through simulations and inferred.

An integrated wireless impulse generator has been designed, simulated, fabricated and tested. Switched oscillator topology has been used as an impulse generator. A switched oscillator consists of a low impedance transmission line, which is charged by a DC source with a large input impedance. The transmission line is connected to a fast closing switch at one end and a high feed-point impedance antenna at the other end. After charging the transmission line, closing the fast switch short circuits the transmission line, resulting in a transient wave propagating toward the antenna. The mismatch between transmission line characteristic impedance and the antenna feed point impedance causes a reflection at the antenna terminal. Due to the short circuit at switch terminal, the reflected signal will reflect back at the switch terminal as well. This back and forth reflection generates a series of pulses at the antenna terminal which will be radiated by the antenna. The switched oscillator impulse generator is designed to operate in the industrial, scientific and medical (ISM) radio frequency band.

In this article, a novel Hexagonal Split-Ring Resonator enclosed Circular Split-Ring Resonator (HSRR-CSRR) inspired printed antenna is presented for sub-6 GHz 5G NR and IEEE 802.11ba/be applications. The proposed antenna comprises an HSRR-CSRR and a D-SHSRR metamaterial unit cell with a partial ground plane. The designed antenna is printed on a low-cost FR-4 substrate with dielectric constant εr of 4.4, thickness of 1.6 mm, and loss tangent of 0.02. An HSRR-CSRR metamaterial structure is designed to get the three distinct resonance frequencies at 3.5 GHz, 5.05 GHz, and 6.2 GHz, respectively. To cover the entire band of Sub-6 GHz 5G NR (5-6 GHz), a Double-slit Single Hexagonal Split Ring Resonator (D-SHSRR) is designed for 5.8 GHz and loaded along with the HSRR-CSRR. The operating principle, equivalent circuit, and parametric extraction of the HSRR-CSRR structure are examined. Compared to the conventional antenna, the proposed antenna has a compact size of (0.38λ_g×0.52λ_g×0.03λ_g). The antenna parameters have been investigated using Ansys HFSS 15.0 software. The measured and simulated results are in good agreement.

This paper presents an efficient method to redesign a horn-fed, double-curvature reflector antenna. It helps reconstruct or repair the reflector according to a correct reference or analyze its radiation characteristics through full-wave electromagnetic simulations. The proposed method mainly consists of five stages. At first, it is necessary to obtain initial data in the form of three-dimensional coordinates of a sufficient number of points sampled from the reflector's different surface areas, especially from its central section curve and its peripheral contour. Then, the best-fitting surface to the sampled points is found using geometrical-optics (GO)-based formulations in an invasive weed optimization (IWO) algorithm. The GO relations extend the reflector laterally using elevation angle, horizontal, or focal point strips. As these are intrinsic formulations for designing doubly-curved reflectors, the fitted surface can resolve the possible defects in the reference reflector's geometryor inaccuracies in the sampled information partly. For this purpose, the reflector's central section curve is estimated by fitting a fifth-degree polynomial curve to the data sampled from it. Also, two kinds of errors, which are based on Euclidean distances, define the optimization algorithm cost function for more reliable surface fitting. In the third stage, the fitted surface's peripheral contour is adjusted to match the outline of the reference reflector using the points sampled from this section. In stage four, the redesigned reflector in the form of a point cloud is converted to a .stl file format for further simulation in a full-wave electromagnetic software. Finally, the similarity between the redesigned and reference reflectors' radiation patterns is examined using a radiation-based cost function in an iterative process, and the previously devised four stages repeat until appropriate results are obtained. In particular, an already designed and fabricated UHF band, doubly-curved reflector antenna, capable of generating a cosecant-squared radiation pattern in the elevation plane and narrow in the azimuth, is redesigned using 99 points sampled from it. It is found that horizontal strips can best fit the reflector with the small normalized error about 3 mm at the end of the IWO algorithm, indicating a nearly perfect geometrical similarity between the redesigned and reference reflectors. For further verification of the suggested method, the redesigned reflector's radiation pattern is simulated in CST simulation software, and the results are compared with the measured radiation pattern of the fabricated reflector and the simulated radiation pattern of the antenna's initial CAD model in the azimuth and elevation planes. Specifically for the redesigned antenna, the amounts of HPBW and sidelobe level in the azimuth plane are about 2.6° and 29.85 dB, respectively. Also, the amounts of gain, HPBW, and predefined parameters of α and β in the elevation plane are 28.25 dB, 13.5°, 5.07 dB, and 11.7°, respectively. All of the measured and simulated results are in good correspondence with each other, suggesting that the proposed method is a secure solution for redesigning double-curvature reflector antennas precisely and efficiently.

Valve radiator blockage is a serious problem endangering the safety of thyristor. At present, there are no effective methods for blockage evaluation and monitoring. This paper analyzes the heat dissipation state of a radiator under different blocking conditions and divides it into abnormal heat dissipation and normal heat dissipation. Then, based on reliability theory, the tolerance index ψ for blockage and the probability index θ for overheating are proposed to evaluate the blockage hazard of the thyristor. Also, the thermal circuit model of the valve group is established to monitor radiator blockage. According to the model, the corresponding relationship between radiator blockage and valve temperature distribution is solved, and the blockage detects index based on device temperature is given to judge radiator block. Through the infrared monitoring temperature solution, judgment of radiator blockage is consistent with the set blockage.

A bearingless induction motor (BL-IM) is a new type of motor integrating suspension and rotation functions. Higher requirements are put forward for its suspension performance. Due to the material advantages of a new type of amorphous alloy with high magnetic conductivity, low loss and low coercivity, it is considered to be used in the BL-IM rotor to reduce iron loss and improve the electromagnetic performance of the BL-IM. Finite element analysis software is used to analyze the performance of two different kinds of motors with the rotors made of conventional silicon steel and amorphous alloy respectively. The magnetic field density distribution, torque, speed, and radial force are compared between the two motors. The results show that the speed of amorphous alloy motor increases faster, and the rotor has better suspension characteristics. Moreover, the amorphous alloy material has a smaller density; the material properties can effectively reduce the weight of the motor; it is beneficial to the operation of the BL-IM in special environments.

Alzheimer's disease (AD) is a degenerative disease of the nervous system that often occurs in the elderly. As magnetic resonance imaging (MRI) and positron emission tomography (PET) reflect the brain's anatomical changes and functional changes caused by AD, they are often used to diagnose AD. Multimodal fusion based on these two types of images can effectively utilize complementary information and improve diagnostic performance. To avoid the computational complexity of the 3D image and expand training samples, this study designed an AD diagnosis framework based on a 2.5D convolutional neural network (CNN) to fuse multimodal data. First, MRI and PET were preprocessed with skull stripping and registration. After that, multiple 2.5D patches were extracted within the hippocampus regions from both MRI and PET. Then, we constructed a multimodal 2.5D CNN to integrate the multimodal information from MRI and PET patches. We also utilized a training strategy called branches pre-training to enhance the feature extraction ability of the 2.5D CNN by pre-training two branches with corresponding modalities individually. Finally, the results of patches are used to diagnose AD and progressive mild cognitive impairment (pMCI) patients from normal controls (NC). The experiments were conducted with the ADNI dataset, and accuracies of 92.89% and 84.07% were achieved in the AD vs. NC and pMCI vs. NC tasks. The results are much better than using single modality and indicate that the proposed multimodal 2.5D CNN could effectively integrate complementary information from multi-modality and yield a promising AD diagnosis performance.

We demonstrate that the future sixth generation (6G) radio links can be utilized for sub-THz frequency imaging using narrow beamwidth, high gain, lens antennas. Two different lenses, a bullet or hemispherical shape, were used in radio link setup (220-380 GHz) for an imaging application. Lenses performed with the gain of 28 dBi, 25 dBi, and narrowed the beamwidths of 1° and 2.5°. Plants were used as imaging objects, and their impacts on radio beams were studied. For assessment, the radio link path loss parameter was -48.5 dB, -53.2 dB, and -57.1 dB with the frequency 220 GHz, 300 GHz, and 330 GHz, respectively. Also, the impact of the radio link distance on the imaging was studied by 50 cm and 2 m link distances. In addition, the 3D image was acquired using the phase component of the image, and it showed the leaf surface roughness and the thickness, which was similar to the measured value.

Beamforming can steer the mainlobe of the beam pattern towards the desired signal and set several nulls in the directions of interference signals by adjusting the excitation weights of array elements. These days, a range of meta-heuristic algorithms have been utilized for beamforming of antenna arrays. However, most of the methods are applied to linear arrays and rarely to planar arrays. In this paper, a novel variant of binary particle swarm optimization (BPSO) is proposed at first, where the global search ability and the local optimization ability are both taken into account. Then, the fitness function including the term of peak sidelobe level (PSLL) is constructed, and the improved BPSO is applied to the beamforming of uniform planar array (UPA). Finally, simulation results demonstrate that the proposed algorithm is not only able to suppress PSLL effectively, but also able to form deeper nulls than that of linearly constrained minimum variance (LCMV).

A novel wide beamwidth microstrip patch antenna fed by a 1:5 unequal Wilkinson power divider with a low profile of 0.027λ₀ is presented. A circular patch and an independent feeding concentric metal ring can realize the broad half-power beamwidth (HPBW) in the far field. A 1:5 unequal Wilkinson power divider is designed as the antenna feed. The HPBWs of the antenna reach 258° and 267° in XZ-plane and YZ-plane, respectively, covering the whole upper half space at central frequency (2.54 GHz). The results of simulation and measurement show great consistency.

Nowadays, due to the ever-increasing number of electronic devices and communication systems that use high-frequency electromagnetic waves, a significant level of electromagnetic energy is available in the environment that is not entirely used. In this work, a complete electromagnetic harvesting system using a rectenna is proposed to collect this energy and feed a temperature measurement module. The rectenna is constituted by a combination of a microstrip antenna that captures the electromagnetic energy and a rectifier circuit that converts it into electric energy in direct current (DC) form to feed ultra-low-power loads. The proposed system uses a rectangular microstrip antenna, designed and optimized by using the Computer Simulation Technology (CST^®) software to operate at 2.45 GHz. This designed antenna presents a measured reflection coefficient lower than -20 dB at the operating frequency with a maximum gain equal to 7.26 dB. In addition, a voltage doubler rectifier circuit is designed and optimized by using the Advanced Design System (ADS^®) to match the impedance of the designed antenna to reduce the reflection losses between these two modules, achieving maximum measured efficiency of approximately 33%. Furthermore, a boost converter circuit is designed for the power management between collected and delivered powers to the sensor and to provide appropriate voltage levels to feed the temperature measurement module. This module consists of an ultra-low-power microcontroller and a temperature sensor that operates in the range of 1.8-3.6 V. The procedures for designing and testing each module of this system are detailed. Finally, a prototype is built and tested under different operating conditions to confirm its functionality and feasibility. These tests show that the proposed system can operate without batteries, only with the harvested electromagnetic energy dispersed in the environment, even from modulated and pulsating sources, as is the case of commercial routers.

A free-space and non-invasive measurement technique to characterize the dielectric properties of a non-magnetic NASA-developed composite material is presented. To estimate the dielectric properties of the composite material, the material under test is placed as a superstrate over a pre-characterized benchmark antenna. The reflection coefficients and gain of the superstrate-loaded antenna are then utilized to estimate the relative permittivity and loss tangent of the composite under test, respectively. Using numerical analyses and measurements of the benchmark antenna loaded with the superstrate, the aforementioned properties are estimated to be 6 and ~0.12, respectively. To validate the accuracy of the method, a square microstrip patch antenna is also designed on a grounded NASA-developed composite material at the ISM band.

This paper proposes an orthogonal dual-feed microstrip patch antenna (MPA) that achieves multi-band resonance along with circular polarization at its primary band of 5G cellular communication. The proposed antenna is simpler than other designs to fulfill extreme data rates and minimum infrastructure requirements. This MPA is designed by taking most care for maintaining the isolation between ports with feasibility for physical fabrication. The HFSS based optimally designed proposed MPA resonates simultaneously at 3.48 GHz (3.3 GHz-3.7 GHz) band, 6.24 GHz (5.925 GHz-6.425 GHz) band, and 7.5 GHz (7.11 GHz-7.9 GHz) bands. The modes achieved for these three bands are TM₀₁, TM₁₁, and TM₁₂ for 3.48 GHz, 6.24 GHz, and 7.5 GHz, respectively. The bandwidths achieved for the bands mentioned above are 160 MHz (4.57%), 330 MHz (5.27%), and 340 MHz (4.53%), respectively. The corresponding gains achieved are 9.8 dB, 5.06 dB, and 7.58 dB. The proposed MPA structure prototype is fabricated, and its performances are measured. The measured S11 for fabricated MPA is close to the resonating frequency found using HFSS simulation. The proposed MPA structure is also modeled and simulated in a MATLAB simulation environment. Performance parameters of the proposed MPA obtained in MATLAB and HFSS are compared and matched reasonably. The proposed MPA structure and its arrays are used for 5G cellular sites as a real-time application in a MATLAB simulation environment. Different test scenarios are created in MATLAB. SINR is visualized for the entire cellular area, and signal strengths are also fetched at the receiver sites.

This paper presents a paattern synthesis method to generate dual-beam patterns of a rectangular planar array of isotropic antennas in a particular scanning angle using Evolution Algorithms. The dual-beam patterns are cosec₂ pattern and pencil beam pattern, and both the patterns are steered to an elevation angle of 20 degrees (θ = 20˚). Moreover, each pattern is synthesized in three azimuth planes (φ = 0˚, 5˚, and 10˚). The isotropic elements are uniformly spaced, and nonuniform excitations are applied to achieve the desired patterns. These patterns are obtained by applying the optimum set of common elements amplitude and phases for the cosecant-squared pattern only. The optimum 4-bit discrete amplitudes and 5-bit discrete phases are produced using using Differential Evolutionary (DE) Algorithm, Genetic Algorithm (GA), Particle Swarm Optimization (PSO) Algorithm, and Firefly Algorithm (FA). These discrete excitations are helpful to reduce the Dynamic Range Ratio (DRR) and the design complexity of the feed networks. The excitations are also verified in a range of arbitrarily chosen azimuth planes. The patterns are generated in the same steering angle with minor variations of the desired parameters. The outcomes established the superiority of DE over PSO, GA, and the effectiveness of the proposed method.