This paper theoretically describes a new concept of passive contactless concentric magnetic gear, which, unlike the existing ones, does not use any separate modulator structure, and instead, a set of strength modulated permanent magnet pole pieces are introduced on the outer permanent magnet rotor structure. Mathematical analysis shows that stable operation in this proposed system is possible with any specific gear ratio, dependent on the number of pole pieces and on the choice of modulation constant of the pole strength variation. The system described is simpler because of the absence of separate modulator structure. The concept is new, leads to less parts count, and hence deserves consideration due to its simplicity. A simple simulation study result is also included at the end, which confirms the presented theory. The main contribution of the paper is the introduction of a new concept for designing magnetic gears using fewer physical components and showing that it is a viable design and able to produce a tangible toque at a particular gear ratio. In addition, the mathematical theory in the paper leads to interesting new results indicated in the design section of the paper, which have not been seen in the literature known to the author.

An innovative methodology for the design of dual-band microstrip monopole antennas is presented in this work. It leverages on the unconventional modeling of the radiator shape based on the perturbed Minkowski fractal in order to fit arbitrarily-defined resonances. A System-by-Design (SbD) technique is exploited to solve the arising global optimization problem with high computational efficiency. Representative benchmarks are reported to assess the effectiveness, reliability, and efficiency of the proposed synthesis approach.

The computation of the fields scattered by a dielectric sphere illuminated by a plane wave and the evaluation of the resultant optical forces is a classical problem that can be analytically solved using Mie theory. Whereas extending said formulation to arbitrary incident fields does not pose any conceptual difficulty, the actual computation of the scattering coefficients and force components substantially grows in complexity as soon as interactions beyond the electric dipole arise. By formulating an equivalent electromagnetic problem, we derive a set of computationally efficient formulas for the evaluation of scattering and optical forces exerted by arbitrary incident fields upon dielectric spheres in the Mie regime. As opposed to force calculations by direct integration of the Maxwell’s Stress Tensor, the present formulation relies on a set of universal interaction coefficients that do not require any problem-specific integration and can therefore be all precomputed and tabulated. The proposed methods can be easily integrated with the T-Matrix method to calculate forces on non-spherical dielectric objects.

In this paper a multifunctional patch antenna loaded with near zero index refraction metamaterial (NZIM) is presented. This multifunctional antenna operates at 5.8 GHz and provides high gain and beam steering capability. The proposed configuration comprises a patch antenna placed below an NZIM superstrate. The rectangular microstrip antenna is used as a radiation source to demonstrate the performance of this design. The NZIM superstrate, which behaves as an NZIM, based on 9×9 resonating unit cells of split ring resonators (SRRs), allows gathering radiated waves from the antenna and collimating them toward the superstrate's normal direction, which results in gain enhancement. The beam-steering in the E-plane is obtained by slowly tilting the NZIM over the patch antenna. The main characteristics of the antenna placed near the NZIM superstrate are studied numerically and experimentally to successfully demonstrate this dual function feature. It is found experimentally that the gain enhancement of 8 dB with improved directivity and radiation efficiency are obtained in comparison with the antenna without the NZIM metasurface. In addition, we were also able to steer the direction of the main beam just by tilting the NZIM superstrate from -20° to 20° with a gain variation of 5 dB and without changing the whole dimension of the structure.

The study investigates the mathematical background of the method of auxiliary sources (MAS) employed in electromagnetic diffraction. Here, the mathematical formulation is developed for E-polarized plane wave diffraction by perfectly conducting two-dimensional objects of arbitrary smooth shape, and the comparison with an analytical and a numerical approach is provided in the numerical part. The results reveal a quite high accuracy among all methods. The importance of the study is to develop the complete mathematical background of MAS for two-dimensional TM-polarized electromagnetic scattering problems by conducting objects. Different from the method of moments (MoM) and other integral equation approaches in electromagnetic scattering problems, here the integral equation resulting from the boundary condition on the scatterer is solved by expanding the current density as orthonormalized Hankel's function with the argument of the distance between the scatterer actual and auxiliary surfaces. The approach can be summarized by that first the sources are shifted inside the scatterer and second, the boundary condition is employed as the total tangential electric field is zero on the surface and inside the object. Then, such expansion leads to eliminating the singularity problems by shifting the sources from the actual surface.

A bidirectional, coplanar waveguide (CPW) fed dumbbell-shaped slot antenna with partially reflecting surface (PRS) with parasitic patches for gain, bandwidth, and radiation pattern improvement is investigated. A dumbbell-shaped CPW-fed slot antenna has a dimension of 0.71λ_g x 0.71λ_g x 0.0571λ_g. The proposed antenna is simple in design and has low profile structure. To achieve improvement in bandwidth, gain, and bidirectional radiation pattern, PRS with parasitic patches are placed on top and bottom of antenna at a distance of 0.25λ_g. The proposed design yields wide bandwidth of 4.11 GHz (4.48-8.59 GHz) with percentage bandwidth of 62.89%, S₁₁ ≤ -10 dB, and peak gain of 5.61 dBi. The variation in the gain over desired bandwidth is less than 3 dB. The antenna is fabricated using an FR4 substrate with relative permittivity of 4.4. The measured results corroborate the design and stipulate the proposed structure to be suitable for applications in C Band.

In this paper, the effect caused by the suspension force windings on the torque windings in a bearingless synchronous reluctance slice motor (BsynRSM) is analyzed, and a new slide model observer is proposed to reduce the speed estimation vibration caused by this effect. Firstly, the effect of suspension force windings is analyzed in a Maxwell model. The suspension force windings will generate an asynchronous torque and current, which are similar to superimposing an asynchronous motor on the original motor. And a special Matlab/Simulink model is built. Secondly, the effect of current and torque generated by suspension force windings on speed sensorless is analyzed. The sliding mode observer (SMO) is studied considering the effect of suspension force windings. Simulation result shows that the current generated by suspension force windings of the BsynRSM will cause the estimate speed vibrating with the rotor vibration, and the frequency of speed estimation vibration is much higher than the additional current and torque generated by the suspension force windings. Thirdly, an improved SMO is proposed. By using the improved SMO, the amplitude and frequency of the speed estimation are obviously reduced. Finally, the improved SMO is verified on the experimental platform, which proves the feasibility of the method.

Cellular UHF (Ultra High Frequency) transceiver networks and base transceiver station antenna systems comprise high power phase shifters for changing and adjusting the phases or delays of high-power transmitting signals delivered to antenna elements. In this work, theoretical and practical adjustment method of amplitudes and phases for electronic steering of a phased array antenna pattern are illustrated. In otherwords, a high power phase shifter with an asymmetric power divideris designed. The phases are changed and adjusted progressively, and thus the beam direction changes from -60° to 60°. The UHF phase shifter has been simulated in Advanced Design System (ADS) and CST STUDIO SUITE SPARK3D and measured. The simulations show that the designed and manufactured UHF phase shifter can also handle more than 20 KW and can be redesigned to reach up to more than 100 KW RF (Radio Frequency) power (microstrip/stripline structures) and can control/change phases of transmitting/receiving antennas. The phase shifter can be designed on any low loss substrate. By using this method in planar high power phased array antenna systems, 360° planar beam tilting is also achievable.zzz

We study two array antennas to expand a 3 dB axial ratio bandwidth. Each array is located at a quarter wavelength above the ground plane and analyzed using the moment method. First, we use paired spiral elements fed by balanced parallel lines to avoid unwanted radiation from the feedline. It is found that the antenna shows an axial ratio bandwidth of 30%. Next, the elements are separated and fed by a single feedline to simplify the feed system. It is revealed that the antenna can radiate a circularly polarized wave under a feedline radiation of less than -16 dB. The frequency responses show that an axial ratio < 3 dB and VSWR < 2 are obtained in a bandwidth of 21%, where the gain is more than 13.3 dBi. The simulated results are verified with experimental ones.

Wave probing systems are used to obtain 2D or 3D images of objects. According to the nature of the waves used (acoustic-microwave and others), these waves can penetrate the fabrics or barriers that are in their way, so it is possible to photograph hidden objects. A system for ultrasonic wideband probing in air with multiple transmitters and multiple receivers with parallel digitization of signals from the receiving array using undersampling is proposed. Probing at frequencies from 38 kHz to 43 kHz is considered when receiving array signals are digitized at a frequency of 18 kHz. Transmitter and receiver placements have been optimized to minimize artifacts and noise. the transmitting and receiving arrays are located at the same plane. The presented results of the experimental study confirm that the processing of measured signals based on spatially matched filtering makes it possible to visualize scattering objects in the environment, including those hidden behind sound-permeable barriers.

Aiming at the problem of poor identification accuracy in traditional particle swarm optimization algorithms, an adaptive search particle swarm optimization algorithm (ASMDRPSO) method for permanent magnet synchronous wind generator (PMSWG) parameter identification is proposed. Firstly, in order to solve the issue of the under-rank equation, a full-rank state equation and fitness function are established. Then, in ASMDRPSO, a dynamic adjustment strategy is adopted in the inertia weight update process to enrich population diversity. In addition, the average best position strategy is designed to avoid getting stuck in a local optimum. Moreover, an adaptive learning radius is supplemented in ASMDRPSO, and the particle search range is enlarged when the ASMDRPSO evolution is stalled. Finally, the simulated and experimental results are presented to verify the stronger optimization ability, stronger robustness, and higher search accuracy of the proposed control strategy than the traditional PSO.

A study of the impact of mutual coupling effects in a co-located multiple input multiple output (MIMO) radar system is presented. Predicted and measured results corroborate that the active reflection coecient (ARC) and beampatterns are impacted by the excitation of each sub-array, the geometric configuration, and their polarization. A uniform linear array (ULA) and a uniform planar array (UPA) layouts are considered. The excitations used in the study are linear frequency modulation (LFM) and Doppler division multiple access (DDMA). A thorough analysis is presented to understand the effects these parameters have on the ARC and on the beampatterns of the radar system.

Partitioning large planar antenna arrays into smaller subarrays reduces the system costs and gives many other advantages. In this article, symmetrical T-shaped tetromino subarrays are suggested to perform the partition process of the large planar arrays. Different structures of T-shaped tetromino subarrays have been obtained by simply rotating its orientation by multiple angles of 90 degrees such that the entire planar array aperture can be filled. Two array architectures based on different T-shaped tetrominoes are constructed. The amplitude weights of the designed subarrays are optimized by means of the genetic algorithm such that the resulting array patterns have low sidelobe level. In the first architecture, all the elements in the original array are divided into several subarrays based on three T-shape structures, while in the second architecture all the elements are combined into eight different T-shapes. To control the sidelobe level in the proposed T-shaped tetromino subarrays, a surface mask boundary function is included in the optimization process to find the optimum weights of the T-shaped subarrays. Simulation results showed that the sidelobes can be reduced to less than -20 dB in the first architecture, and less than -25 dB in the second architecture, in addition to a significant reduction in the complexity of the feeding network for each one. Moreover, detailed connections of the feeding network circuitry of the used T-shaped tetromino subarray structures are given for practical implementation.

In this paper, a polarization-insensitive and dual-band Electromagnetic Induced Transparency-Like (EIT-Like) metamaterial is proposed, which is made of a cross-shaped graphene structure. Due to the mutual coupling between intralayer and interlayer, two high transmission windows can be obtained in different frequency bands. The sensibilities located at the two transmission peaks are calculated as 0.385 THz/RIU and 0.979 THz/RIU respectively. In addition, the maximum group index of 174.5 is obtained. By adjusting the Fermi level of graphene, the transmission and group index could be modulated independently. The characteristics make the proposed metamaterials possess the potential as a tool for biological detection, slow light technology, and filters in THz region.

In this paper, the electromagnetic vibration characteristics of hybrid excitation double-stator Bearingless Switched Reluctance Motor (HEDSBSRM) used in flywheel battery are analyzed when the rotor is eccentric. Firstly, the influence of rotor eccentricity on motor vibration is theoretically analyzed. Then the finite element method is adopted to study the radial electromagnetic force of the motor in the two-dimensional air-gap region. In addition, the three dimensional equivalent vibration model of the motor outerstator is established, and the mode shapes and natural frequencies of the motor stator are obtained by the modal analysis. The vibration characteristics of the outer stator under eccentric motion are analyzed by the coupling calculation of electromagnetic field and mechanical field. Finally, the modal combination principle is used to analyze the vibration characteristics of the motor running at multiple speeds under eccentric condition. The results show that the vibration of HEDSBSRM is closely related to eccentricity, which affects the motor performance and lays the foundation for the optimization design of HEDSBSRM application in flywheel battery.

This manuscript refers to the electromagnetic scattering problem involving plane waves at skew incidence with respect to the edge of a right-angled metallic wedge having one face coated by a double negative metamaterial sheet. Its presence in the propagation scenario is properly accounted at high frequencies by considering the geometrical optics response of the structure and the diffraction contribution arising from the edge of the wedge. In particular, the reflection coefficients related to the coated surface are determined for both the polarizations by using the equivalent transmission line circuit, whereas the diffraction coefficients are obtained by applying the uniform asymptotic physical optics approach. This last is based on electric and magnetic equivalent surface currents under the physical optics approximation and permits to evaluate the diffraction contribution in the context of the uniform geometrical theory of diffraction. The resulting approximate solution is characterized by the same simplicity of use of the heuristic solutions and provides reliable field values as confirmed by the numerical tests carried out by a full-wave commercial software.

A simple balanced bandpass filter is presented. It is constructed mainly by a loop-type resonator with loaded shorted/opened stubs. The resonator is fed by the balanced coupled-line structure. In the loop-type resonator, three approaches can be simultaneously utilized to achieve high common-mode suppression. One is that the loop-type resonator has different differential/common-mode resonant frequencies, which results in a good in-band common-mode suppression. The second is that the loaded short stubs with different lengths will make the input/output port couplings to have different coupling strengths, which will deteriorate the common-mode bandpass response. The third is that loading the grounded resistors can effectively dissipate the common-mode signal. Meanwhile, loading the grounded resistors in the balanced coupled-line structure can effectively dissipate the reflective common-mode signal. A detailed description about its structure, operational mechanism and design method is given. For demonstration, a prototype balanced bandpass filter working at 2.4 GHz is designed, fabricated and measured. A high in-band common-mode suppression of 49 dB is achieved. The measured and simulated results can verify the effectiveness of the proposed balanced bandpass filter and the design method.

Most of the works on sparse array synthesizing via the compressed sensing (CS) approach assume that the active elements exactly lie on the predefined grids. In fact, grid-mismatch error is unavoidable when an array aperture is discretized into grids, and the synthesizing results largely depend on the density of the grids. To overcome this limitation, an innovative off-grid CS approach is proposed for jointly estimating the excitations and positions of array elements. The synthesis problem is specifically formulated using a ridge regression model based on dynamic grids. The candidate positions of elements are treated as variables rather than constants predefined by discretization. Numerical experiments are conducted to validate the effectiveness and flexibility of the proposed method in realizing several maximally sparse arrays meeting the targeted patterns, i.e., the focused and shaped beam patterns of 1-D and 2-D arrays.

Compact wireless devices have been proposed as a result of the introduction of wireless communication systems, allowing more space to be used for other electronic components. A reconfigurable antenna is critical in today's cutting-edge wireless technologies. Reconfigurable antennas can perform a variety of tasks depending on their operating frequency, radiation pattern and polarization. Dynamic tuning can be done by altering mechanical, electrical, physical, or optical switches to run a certain switching mechanism. This can be accomplished using a single reconfigurable antenna that allows the user to customize a range of performance attributes such as resonant frequency, polarization and radiation pattern to meet their specific requirements. This paper looks into different types of reconfigurable antenna switching mechanisms, different types of effective implementation techniques, different types of reconfigurable antennas, and some recently proposed reconfigurable antenna designs for the Fifth Generation (5G) and IoT applications in various wireless communication systems.

Flux reversal machines (FRMs) have a broad application prospect due to its simple structure, high efficiency, and high reliability. However, due to the large magnetic flux leakage between poles, the further improvement of torque density of the FRMsis limited. To reduce magnetic flux leakage and improve torque, a novel consequent pole FRM with asymmetric stator poles is proposed in this paper. The `NS-NS' arrangement order of thepermanent magnets (PMs) of the conventional FRM is changed to the `NSN-S' PMs arrangement order with asymmetric stator poles, and the consequent pole topology is used simultaneously. All the N-poles of PMs are replaced by iron poles. Finally, the topology of the `Fe/S/Fe-S' arrangement order is obtained. A simplified magnetic circuit model is established to explain the principle of reducing magnetic flux leakage. To improve the torque density, the key design parameters are optimized by genetic algorithm, and the optimal parameters of the machine are finally determined. Finally, the finite element model is established. Compared with the conventional FRM, the torque of the proposed machine is increased by 67.18%, and the consumption of PM is reduced by 51.6%. Therefore, the proposed machine has good electromagnetic characteristics and economic benefits.