This article proposes a compact microstrip four-port dual circularly polarized (CP) multiple-input multiple-output (MIMO) antenna with polarization diversity for Sub-6G band. The proposed MIMO antenna consists of four antenna elements, two of which are left-hand circular polarization (LHCP), and the other two are right-hand circular polarization (RHCP). The circular polarization of each antenna element of the MIMO antenna is achieved by a microstrip feed line and a slotted ground plane with two rectangular strips. A novel decoupling element of the antenna composed of I-shaped and II-shaped metal strips is cross-connected and merged between the ground planes of the antenna to obtain wide axial ratio bandwidth and high isolation. The size of the proposed antenna is 55×55×1.6 mm³. The antenna of the impedance bandwidth (S₁₁ ≤ -10 dB) is 3.28-3.80 GHz (14.6%), and the axial ratio bandwidth (AR ≤ 3 dB) is 2.85-3.87 GHz (30.3%). Inter-element isolation less than -16 dB and the envelope correlation coefficient (ECC) less than 0.07 are achieved between the ports of the antenna. The proposed MIMO antenna achieves full coverage of CP characteristics within the impedance bandwidth. The proposed antenna is beneficial to the application of Sub-6G band. At the same time, it is also suitable for dual circular polarization communication and polarization diversity system.

A higher degree of miniaturization technique is presented based on frequency reduction method for a rectangular patch antenna by introducing slot on the radiating patch with unchanged antenna configuration. To realize the frequency reduction technique, a rectangular patch is design to operate at the fundamental frequency. Then a slot on the radiating patch is introduced and as an effect of slot, fundamental resonant frequency is shifted in left side in reflection coefficient plot. The percentage of reduction resonant frequency is 65.80% where 2.31 GHz is the fundamental frequency, and 790 MHz is the operating frequency of slot integrated patch geometry. In addition, we introduced another similar slot on the ground plane, and as a result, resonant frequency shifted from 790 MHz to 729 MHz caused by 68.44% reduction in resonant frequency with unchanged antenna dimension. Equivalent circuits have been analyzed for each antenna topology. To verify the simulated results, prototypes are fabricated and complied with measured results.

This study provides an alternative and straightforward approach to determining buried dielectric objects underground by employing the method of auxiliary sources. In the direct scattering problem, the Brewster angle is determined, and then the electromagnetic properties of the ground are determined. Later, the scattered field above the ground due to the buried object is evaluated. The localization of the buried object is obtained by the continuity of the field components while solving the inverse problem. The numerical experiments are done, and outcomes of the numerical experiments are compared with a commercial full-wave computational electromagnetic software. The outcomes reveal less than 1% deviation between the proposed approach and the commercial tool.

The impact of permanent magnet (PM) properties such as magnetremanence and coercive force or coercivity on the electromagnetic output of flux-switching permanent magnet machine having C-core stator topology is presented and compared in this work. A two-dimensional finite-element analysis (2D-FEA) approach is implemented using ANSYS-MAXWELL software package. Three-dimensional (3D) FEA calculations are also conducted, in order to realize more accurate results, and its results are compared with the 2D-FEA predicted results. The investigated machine elements are: airgap flux-density, torque ripple, total harmonic distortion (THD) of the voltage, cogging torque, unbalanced magnetic pull (UMP) or force, winding inductances, direct- and quadrature-axis flux, electromotive force and output torque. The analyses show that undesirable qualities such as large amount of cogging torque and UMP are predominant in the machine having rare-earth magnets i.e. neodymium and samarium-cobalt, although they have larger flux linkage and superior average torque compared to its non-rare-earth magnet equivalents i.e. the ferrite- and alnico-made machines. Moreover, the alnico- and ferrite-made machines exhibit larger winding inductance values, and consequently lower saturation withstand capability, though with better field-weakening capability. Further, the predicted efficiencies of the compared machine types having alnico, ferrite, neodymium and samarium materials, at rated current and speed conditions are: 79.8%, 75.76%, 87.22% and 86.58%, respectively. More so, the generated electromagnetic output power of the compared machine types at the operating base speed is: 206.57 Watts, 186.57 Watts, 449.67 Watts and 396.40 Watts, respectively. The investigated machine is suitable for high torque in-wheel direct-drive applications.

In this paper, the mutual coupling from a multiple-input-multiple-output (MIMO) rim antenna has been utilized to control the level of specific absorption rate (SAR), when the mobile handset comes in close contact to the human body. The proposed antenna is capable of operating at 2.1 GHz and 4.3 GHz, respectively. A periodic defective ground structure (DGS) in conjunction with diodes and capacitors are used to manipulate the coupling between antenna elements. The working of the proposed dual band antenna design is validated using the characteristic mode analysis (CMA), and the current distribution. The MIMO performance is studied by using envelope correlation coefficient (ECC) and loss in capacity analysis. The effect of hand and LCD on the antenna performance is shown. The SAR analysis shows up to 30% reduction, in comparison to the baseline value of the SAR of the proposed antenna design.

A novel ultra-wideband (UWB) antenna with triple band rejection capabilities operating in quad bands is presented. The proposed UWB antenna is derived from a planar rectangular shaped monopole antenna. In order to improve the bandwidth ratio of the antenna, a partial ground is maintained with a slot at centre along with truncated slots made at bottom two corners and a rectangular slot at top side centre of the radiating patch. In order to achieve the required triple notch characteristics and the multiband operation, a single meander line slot is made in the middle of the patch. The dimensions of the meander line slot are varied to change the notch band characteristics of the antenna. The FR4 substrate with dielectric constant 4.4 with thickness of 1.6 mm is used to design the antenna. The overall size of the antenna is maintained compact with dimensions 40 mm×38 mm. The proposed UWB antenna rejects triple bands 3.29 GHz-4.83 GHz (WiMAX), 5.15 GHz-6.84 GHz (WLAN), & 7.94 GHz-8.49 GHz (X-band satellite uplink). The operational bands of the UWB antenna with triple notch bands are as follows, 2.38 GHz-3.29 GHz, 4.83 GHz-5.15 GHz, 6.84 GHz-7.94 GHz, and 8.49 GHz-13.15 GHz. The measured peak gains at 2.7 GHz, 5 GHz, 7.3 GHz, 8.7 GHz, and 11.5 GHz are 3.4 dBi, 2.8 dBi, 3.6 dBi, 3.3 dBi, & 3.88 dBi, respectively. The step-by-step implementation of the triple notch band UWB antenna and the comparative analysis is presented. The proposed antenna performance is presented with the help of reflection coefficient, VSWR, gain, field distributions and radiation pattern curves. The simulated and measured analysis comparison shows good agreement making the designed antenna a good candidate for UWB applications that require multiband operations with selected bands rejection.

Six-pole hybrid magnetic bearing is a multiple input-output system with strong coupling between the degrees of freedom, a state feedback linearization dynamically decoupling the fuzzy immune PID controller for the subsystem after linear resolution coupling is proposed in this paper. Firstly, the basic theory of linear resolving coupling is expounded. Secondly, the proposed decoupling theory and control strategy are simulated in Matlab. Finally, the experimental platform is built, and the suspension experiments and coupling experiments are performed. It can be seen that the fuzzy immune PID controller has good performance, and the state feedback linearization method can realize the decoupling between the radial degrees of freedom of six-pole magnetic bearings.

A fractal antenna with enhanced bandwidth (BW) from 2.62 GHz to 5.2 GHz is presented for Wi-Fi applications. The antenna is designed to achieve a wider BW, and it consists of a rectangular shape patch attached to a half circular disc. The antenna is fed by microstrip feed model. The ground plane of the antenna is maintained partial with a slot at centre. Double head arrow cross shaped slots are etched on the radiating element to form the proposed fractal antenna. While the centre slot is made to look like + symbol, the surrounding four fractal slots are made to look like × symbol. FR4 substrate with dielectric constant 4.4 with thickness 1.6 mm is used to design the antenna. The overall size of the antenna is maintained compact with dimensions 44 mm × 40 mm. The dimensions of the fractal slots are varied, and the operating band is tuned. The proposed antenna covers from 2.62 GHz to 5.2 GHz with BW 2.58 GHz. The step-by-step implementation of the fractal antenna and comparative analysis are presented with the help of reflection coefficient curves. While the proposed antenna covers wideband, it showed peak resonance at dual operating frequencies at 3.2 GHz and 4.8 GHz. The designed antenna-maintained gain of 2.96 dBi and 3.47 dBi at 3.2 GHz and 4.8 GHz frequencies, respectively. The proposed antenna performance is presented with the help of reflection coefficient, VSWR, gain, field distributions, and radiation pattern curves. The simulated and measured analysis comparison showed good agreement making the designed antenna a good candidate for wideband Wi-Fi applications.

The multi-objective optimization of the six-pole outer rotor hybrid magnetic bearing (OSHMB) not only solves the nonlinear and strong coupling problems of the three-pole magnetic bearing (THMB), but also makes the magnetic bearing structure more compact and improves the maximum bearing capacity. Firstly, the structure and working principle of the OSHMB are introduced, and the mathematical models of suspension forces are established by the Maxwell tensor method. Secondly, the key parameters of the OSHMB are multi-objective optimized, and an optimal set of parameters is obtained through the sensitivity analysis, constructing the response surface model, and the multi-objective optimization based on the genetic algorithm. Based on the optimal parameters, the force current characteristics and maximum carrying capacity of the OSHMB are analyzed. Finally, the experimental platform is built. The suspension experiments, anti-interference experiments and load loading experiments are performed. It can be seen that the maximum bearing capacity of the OSHMB is about 9.6% higher than that of the SHMB.

For full duplex communication, a signal parallel transfer method based on partial power transmission couplers is proposed in this paper. The power transfer uses a serial LC compensation structure topology, and the data transmission channel adopts a double coupling resonant circuit. In terms of power transmission, some power coupling inductors and power compensation capacitors form a power resonance network with a high frequency trap function, which can isolate the influence of signal transmission. Therefore, there is no need for an additional trap, which reduces power loss and the space occupied by the structure. In terms of signal transmission, the partial coupling coil method can increase the coupling frequency and the data transfer rate. In addition, the signal transmission circuit has the characteristics of dual resonance frequencies. The forward and reverse signals modulate the carrier at different resonance frequencies to realize full duplex communication. Finally, the simulation results prove that the scheme is practicable for full duplex communication and parallel transmission of power, achieving anoutput power of 1.4 KW, and the highest transmission rate can reach 1 Mbps.

A dual-polarized wide-angle scanning array antenna is proposed in this paper. The proposed antenna array consists of sixteen elements with the working band from 9.5 to 10.5 GHz. A microstrip patch fed from two orthogonal directions is applied to achieve dual-polarization. In order to obtain good impedance matching and wide bandwidth of the antenna, capacitive coupling feeding is adopted. The measured results show that the proposed array can cover a wide scanning range of ±58°. The polarization isolations of antenna are higher than 17 dB. The isolations between receiving sub-array and transmitting sub-array are higher than 22.3 dB. The proposed array antenna is suitable for Van Atta applications.

In this paper, a novel tunable LC bandpass filter (BPF) based on LC magnetic-dominant mixed coupling is proposed. The design equations for the coupling coefficient and resonating frequency are given. The magnetic dominant coupling region and electric dominant coupling region are studied. The magnetic-dominant mixed coupling is used to compensate the bandwidth of the tunable filter, so that the tunable filter with constant absolute bandwidth can be obtained. The filter is designed, simulated and measured, and the measurement matches the simulation very well. The measurement shows that the central frequency tuning range is from 72 MHz to 222 MHz with -3dB bandwidth of 16.5±3.5 MHz.

This paper proposes a novel miniaturized interdigital capacitor loaded interdigital filter, which is applied in C-band (3.2 GHz~4.2 GHz). By loading an interdigital capacitor on the open end of the resonator of the interdigital filter, the length of the resonator is shortened by 28%. The resonant frequency offset caused by tap introduction is adjusted by using the method of impedance compensation at the open end of resonator 1 and resonator 5, which further reduces the size of the filter. The miniaturized filter is fabricated on a 0.254 mm-thickness alumina substrate with relative dielectric constant of 9.8 by thin film process. Measured results are as follows: the passband of the filter is 3.2 GHz~4.2 GHz; the insertion at center frequency is -1 dB; the return loss is less than -18.3 dB. The size of the filter is 4.98 mm*6.45 mm (0.15λ_g*0.20λ_g), which is 37.8% smaller than that of the traditional interdigital filter.

This paper explores a loaded conductor backed coplanar waveguide (CB-CPW) split ring resonator (SRR) fed U-slot planar antenna used for healthcare monitoring via the wireless scientific industrial medical (ISM) band and medical service band at fifth generation (5G-MSB). The antenna has been designed with bio-tissue layers, muscle layers, skin, and fat. The parameters of the designed antennas, such as miniaturization, increased gain, and enhanced bandwidth, are presented. The proposed prototype results in the total size of 640 mm³. Such designed antenna has been operated at (3.4-3.6) GHz - fifth-generation medical service band and at (2.38-2.48) GHz - industrial scientific band and can realize proximately omnidirectional radiation pattern over the operating bands.

This paper presents the application of machine learning-based approach toward prediction of path loss for the large intelligent surface-assisted wireless communication in smart radio environment. Two bagging ensemble methods, namely K-nearest neighbor and random forest, are exploited to build the path loss prediction models by using the training dataset. To generate the data samples without having to run measurement campaign, a path loss model is developed owning to the similarity between the large intelligent surface-assisted wireless communication and the reflector antenna system. Simple path loss expression is deduced from the system gain of the reflector antenna system, and it is used to generate the data samples. Simulation results are presented to verify the prediction accuracy of the path loss predictions models. The prediction performances of the trained path loss models are assessed based on the complexity and accuracy metrics, including R² score, mean absolute error, and root mean square error. It is demonstrated that the machine learning-based models can provide high prediction accuracy and acceptable complexity. The K-nearest neighbor algorithm outperforms random forest algorithm, and it has smaller prediction errors.

Based on the principle of bionics, this paper combines the design of flexible bionic antenna with Chinese culture, and proposes a dual-material bionic antenna with Electromagnetic Band Gap(EBG) structure. The antenna uses a polyimide flexible substrate. Radiation patch of this antenna is shaped like a ``pear flower'', and the ``CHINA'' shaped slot is etched on the ground to form a Logo mark. In order to reduce the impact of antenna radiation on human body, the introduction of an EBG structure made of Polydimethylsiloxane (PDMS) material makes the front-to-back ratio of the antenna radiation significantly increased. The antenna was bent in different ways and was placed on human body model for simulation and testing. The results showed that the antenna achieved an impedance bandwidth of 18.8% (2.22-2.46 GHz), the peak gain was 4.02 dBi, and the antenna was low sensitive to deformation, which makes it suitable for modern flexible electronic equipment.

A Compact wideband operating from 3 to 18 GHz MIMO antenna with quadruple notches is presented in this paper. The elements in MIMO configuration are arranged in orthogonal fashion with each other to minimize the coupling effects. The antenna consists of circular rings and a modified microstrip feed. By engraving a crescent shaped slot, split ring-shaped slot, circle shaped slot in the circular monopole, rectangular spiral shaped slot engraved along the feed line quadruple notches are attained. The antenna operates from 3 GHz to 18 GHz with notches in the range of 3.2 GHz-4.2 GHz centered at 3.5 GHz, 4.5 GHz-5.5 GHz centered at 4.9 GHz, 6.2 GHz-7.3 GHz centered at 6.6 GHz, and 8.1 GHz-8.8 GHz centered at 8.5 GHz. The element has a very compact size of 0.28λx0.22λx0.016λ at 3 GHz and is hence suitable for portable devices.

Beam Collection Efficiency (BCE), sidelobe level outside the receiving area (CSL), and cost are need to be considered in optimizing the transmitting array of a Microwave Wireless Power Transmission (MWPT) system. To solve the problem of too low BCE caused by dividing a small number of subarrays, this paper proposes a novel one-step subarray partition algorithm named Multi-Particle Multi-Parameter Dynamic Weight Particle Swarm Optimization Subarray Partition (MPMP-DWPSO-SP). The algorithm optimizes the position and structure of each element at the same time, and the number of the subarrays is no more than 4. It is verified by simulation that the BCE obtained by using this algorithm to optimize the Sparse Quadrant Symmetrical Rectangular Array (SQSRA) with an aperture of 4.5λ×4.5λ and the array element number of 8×8 can reach more than 90%. In addition, a new intelligent optimization model is designed for dividing the 8×8 array into 2 subarrays, and BCE and CSL can reach 91.69% and -17.61 dB.

We introduce a theory of optical responses of bianisotropic layers with arbitrary effective medium parameters, which results in generalized Fresnel-Airy equations for reflection and transmission coefficients at all incidence directions and polarizations. The poles of these equations provide explicit expressions for the dispersion of Fabry-Perot resonances and surface electromatic waves in bianisotropic layers and interfaces. The existence conditions of these resonances are topologically related to the zeros of the high-k characteristic function h(k)=0 of bulk bianisotropic materials and taxonomy of bianisotropic media according to the hyperbolic topological classes [32, 33].

Since the first working multilevel fast multipole algorithm (MLFMA) for electromagnetic simulations was proposed by Chew's group in 1995, this algorithm has been recognized as one of the most powerful tools for numerical solutions of extremely large electromagnetic problems with complex geometries. It has been parallelized with different strategies to explore the computing power of supercomputers, increasing the size of solvable problems from millions to tens of billions of unknowns, thereby addressing the crucial demand arising from practical applications in a sense. This paper provides a comprehensive review of state-of-the-art parallel approaches of the MLFMA, especially on a newly proposed ternary parallelization scheme and its acceleration on graphics processing unit (GPU) clusters. We discuss and numerically study the advantages of the ternary parallelization scheme and demonstrate its flexibility and efficiency.