Air compressors are widely used in various industrial fields. The motor of air compressor requires high power and high speed. This paper focuses on the structural design and loss analysis method of highspeed permanent magnet synchronous motor in air compressor. The structure of motor is designed. The key parameters are calculated. The influence of structural parameters on motor loss is analyzed. The analytical and design results are verified by finite element method (FEM). Finally, the prototype of motor has been manufactured. The performance of the motor is verified on the prototype.

A small ring antenna working at 2.45 GHz was designed in this paper, a small disk-coupled structure was applied to feed an inner-hole-biased ring patch, contributing to not only improving the impedance characteristics of the antenna but also reducing the size. The simulation results show that the designed patch area is only 70.7% of that of the traditional circular microstrip antenna on the premise of ensuring good bandwidth and gain performance; the -10 dB bandwidth of S₁₁ parameter is 62 MHz; the gain of the maximum direction is 7.11 dB; and the circular polarization of the antenna is also realized. This design has also been compared with several conventional designs, It is proved that the antenna has good comprehensive performance, and the antenna feed structure is simple, easy to process, very conducive to engineering applications. Finally, the feasibility of this technology was verified by contrasting the measured data with the simulation data.

In this paper we present a high pass filter based on half mode substrate integrated waveguide HMSIW technology dedicated to the transmission of microwave signals range from 6 GHz to 18 GHz. The taper is used for microstripe to SIW transition. We designed SIW line transmission using CST and HFSS simulators on a Rogers RT5880 substrate with dielectric constant of 2.2 and thickness of 0.508 mm, and we used the half mode technique for miniaturizing the filter size and achieving a size reduction about of 50%. The fabricated filter size is 60 x 12 mm². The lower measured return loss is about -51 dB. We compared the simulation results with measurement ones for validating our proposal. Good agreement between CST, HFSS and measurement results is observed.

In this paper, a novel low-profile direct feed antenna element is proposed to work across the mm-wave frequency band for 5G smartphone applications. The antenna covers the frequency band from 25-32 GHz achieving a wide fractional bandwidth of 24.5%. Contrary to most of the previously reported designs, the proposed antenna has a low-profile single-substrate structure and uses a conventional corporate feed. To improve the overall gain, a 16-element antenna array is formed based on the proposed antenna element. The total realized gain of the array is 15 dBi, and its size is 63×10×0.64 mm³ which fits inside a smartphone chassis. To validate the idea, a prototype is fabricated and measured. A study is also conducted, through simulations, on the beam steering capabilities of the antenna array using digital phase shifters. Having a simple structure and good performance makes the proposed antenna array an excellent candidate for 5G smartphone applications.

A dual-band dual-polarized dipole antenna with an artificial magnetic conductor (AMC) reflector is proposed, which can be applied in 5G base stations. The antenna consists of a pair of ±45° crossed dipoles and a wideband AMC reflector. By adopting arrow-shaped dipoles and introducing slots, dual-band characteristic is achieved. The AMC is designed to operate with 90° reflection-phase bandwidth of 2.1-3.9 GHz (30%). Compared with using traditional reflector, the profile height can be reduced from 0.25λ₀ to 0.11λ₀ (where λ₀ is the free-space wavelength at 2.6 GHz). The measurement results show that the impedance bandwidth with |S₁₁| < -14 dB is about 15.5% (2.44-2.85 GHz) and 18.6% (3.17-3.82 GHz), covering the Sub-6 GHz bands. The average gain is 8.5 dBi in the lower band and 8.2 dBi in the upper band. At 2.6 GHz and 3.45 GHz, the half-power beamwidth of the antenna is 77° and 80°, respectively. In the two bands, the port isolation of the antenna is more than 28 dB, and the cross-polarization level is less than -20 dB.

A model predictive control method for permanent magnet synchronous motor based on parameter identification and dead time compensation is proposed to solve the problems of poor parameter robustness and large current errors. In this method, the prediction model is firstly established based on the mathematical model of the permanent magnet synchronous motor. After that, the current error caused by the parameter change in the prediction model and the current harmonics caused by the dead time effect are basically analyzed theoretically. Then, the adaptive linear neural network algorithm is proposed to identify the motor parameters and applied to the prediction model, and the harmonic components are filtered out using the adaptive linear neural network algorithm. The recursive least squares algorithm is used to quickly update the system weights to improve the dead time compensation control effect. Finally, the effectiveness and correctness of the proposed algorithm are verified on the experimental platform. The experimental results show that the predictive control method of permanent magnet synchronous motor model based on parameter identification and dead time compensation can effectively reduce the current error of the control system and accelerate the dynamic response of the speed.

A wideband and widebeam magneto-electric (ME) dipole antenna is designed in this paper. Based on the conventional magneto-electric dipole antenna, a bent vertical metal plate is added to the electric dipole, and the impedance bandwidth (IBW) and beamwidth of the antenna are widened together. Inclined metal walls are added on both sides of the metal ground to improve the gain at high frequency and make the antenna gain more steady in the operating bandwidth. To further broaden the IBW of the antenna, the conventional Γ-shaped feed is changed into a branch structure. The IBW of the finally designed antenna reaches 56.8% (2.91-5.22 GHz). In the whole operational bandwidth, the radiation pattern in E-plane realizes the half power beam width (HPBW) of more than 110°, and the H-plane radiation pattern realizes the HPBW of more than 160°. The maximum width of E-plane HPBW is 175°, and the maximum width of H-plane HPBW is 229°.

This paper presents a broadband antenna for 5G indoor micro base station, which has a low profile and simple structure. The proposed antenna avoids the traditional high-cost multilayer technology and is a low-cost configuration. It consists of a center fed circular patch with four shorting pins to properly stimulate the radiation mode of TM₀₁ and TM₃₁ internally. Next, four equally sized fan-shaped slots are opened in the radiator to further expand the bandwidth and improve the input impedance. |S₁₁| < -10 dB simulation impedance bandwidth is about 51% from 3.11 to 5.24 GHz and covers 5G n78 (3.3-3.8 GHz) and n77 (3.3-4.2 GHz) and the n79 (4.4-5 GHz). The voltage standing wave ratio (VSWR) < 1.8 in the whole operating frequency band, which has good matching characteristics.

Radar remote sensing applied to forest covers is a domain of interest for a few decades, particularly in forest monitoring for the global carbon cycle. In this paper, we use a numerical electromagnetic scattering model to investigate the full-inversion of a simple case where two dielectric cylinders are lying upon a metallic ground seen as a theoretical representation of only one tree trunk and one primary branch. The presented process performs cylinders 3D-locations estimation using an Orthogonal Matching Pursuit (OMP) algorithm, then scattering coefficient is retrieved for each cylinder and each scattering mechanism separately and finally the cylinders biophysical parameters (height, radius, complex permittivity) inversion using a Particle Swarm Optimisation (PSO) algorithm. This process is based on target subspace decomposition and applied to noisy simulated radar data.

This paper proposes a 4-port MIMO (Multiple-Input Multiple-Output) antenna operating at 28 GHz in the millimeter wave band for future 5G communications. The first design in this work is a single-element circular shaped microstrip patch antenna with an elliptical slot and a defected ground structure which is intended for 28 GHz band. This antenna is compact with a size of 6 mm × 7 mm. A complete analysis of single patch element antenna is presented with effect of slot and defected ground structure in Section 2. In Section 3, the second design, which is symmetric two-element MIMO slotted circular patch antennas, is analyzed with the dimension L x W as 7 mm x 6 mm. In Section 4, the final fabricated design is presented, which is a 4-port MIMO antenna operating at resonance frequency of 28 GHz along with the improved isolation between the elements due to appropriate spacing. The proposed 4 port MIMO antenna is designed on a Rogers Duroid 5880 substrate having a relative dielectric permittivity of 2.2 and thickness of 0.8 mm. The overall dimension of this designed MIMO antenna is 20×20×0.8 mm³. Simulated results for the S-parameters and radiation pattern are presented for all purposed designs using CST software. Measured results are also presented for the return loss using Rhode & Schwarz ZVA 40 vector network analyzer. Simulated and measured results show a good agreement. The simulation results demonstrate that the return loss at individual port is less than -10 dB in the frequency range of 26.867–28.975 GHz, and it provide a bandwidth of 2.1 GHz. The antenna has a high gain of 9.24 dB with unidirectional radiation pattern, and each element has a mutual coupling less than -20 dB.

Based on a self-consistent Schrodinger-Poisson solver and top-of-the-barrier model, a quantum transport simulator of p-type gate-all-around nanosheet FET is developed. The effects of material (Si/Ge), stress, crystallographic orientation, and cross-sectional size are deeply explored by numerical simulations for the device performance at the sub-3 nm technology node. A strain-dependent 6-band k.p Hamiltonian is incorporated into the model for a more accurate calculation of E-k dispersion in the strain-perturbed valence band structure, where the curvature, energy shift, and splitting of subbands are investigated in detail for hole transport properties. Further, the effect of channel engineering is comprehensively analyzed, by evaluating density-of-states effective mass, average injection velocity, mobility, current density distributions, and the current-voltage characteristics. An effective performance improvement from 2GPa compressive stress is obtained in [100]/(001) and [110]/(001) channels, with a 7% enhancement of ON-current in Ge nanosheet FETs. While a wider channel cross-section improves the drive current by increasing the effective channel width, a smaller cross-sectional width yields an average increase up to 29% in the ON-state injection velocity due to stronger quantum confinement.

One of the main challenges in the application of wireless power transmission systems is to achieve stable power transmission and constant transmission power under dynamically changing coupling conditions. A parity-time symmetric model for AUV (autonomous underwater robot) is proposed. Based on the coupling mode theory, the robustness of the parity-time symmetric wireless transmission system is investigated. The theoretical analysis shows that the AUV wireless power transmission system based on parity time symmetry can automatically obtain constant output power and constant transmission efficiency when the coupling coefficient is varied. Based on this theory, the experimental prototype was built by simulating the effects of relevant parameters using LTspice. And the experiments were conducted in air medium and seawater medium respectively. The experimental results show that under the condition of parity time symmetry, the underwater wireless energy transmission voltage ratio is close to 1, and the transmission efficiency reaches 15%, in the range of 12.5 cm. The theoretical derivation has been verified.

Gap-surface plasmon (GSP) metasurfaces that consist of metallic resonators, a middle dielectric spacer, and a back metallic reflector have become an emerging research area due to their excellent properties, such as ease of fabrication, high efficiency, and unprecedented capabilities of controlling reflected fields. In this concise review, we introduce our efforts in exploring the physical principles and fascinating applications of multifunctional GSP metasurfaces in the optical range. Starting with a typical GSP meta-atom, we present the concept and mechanism of simultaneous and independent phase and polarization control. We then overview some typical applications of GSP metasurfaces, including beam-steering, surface plasmon polariton coupling, metalenses, meta-waveplates, and dynamical metasurfaces. The review is ended with a short perspective on future developments in this area.

In this paper, an optimized circularly polarized (CP) antenna is proposed for operating in the LTE bands 42/43 applications. This CP antenna comprises three sections, the meander-line and L-shaped strip structures modeled on the front side of a Roger 3003 substrate, and on the back side a rotated H-shaped ground plane is printed. In order to further increase the antenna common bandwidth (CBW), that is the voltage standing wave ratio bandwidth (VRBW) and axial ratio bandwidth (ARBW), an offset-fed line on the front side and a shorting pinare used. A feasible solution of the optimized CP antenna with compact size is achieved by applying an optimization design methodology with a fitness function that takes into account the antenna performance parameters, CBW or both the VRBW and ARBW in addition to the realized gain (RG). Two programs are operating in synchronous fashion for finding the optimal geometric antenna parameters, a particle swarm optimization (PSO) for implementing the fitness function in MATLAB and a CST MWS simulator tool for extracting the antenna performance parameters. The optimized antennas without and with shorting pin are obtained with a broadest CBW and feature of CP operation and an acceptable RG across the desired LTE 42 (3.4-3.6 GHz) and LTE 42/43 (3.4-3.8 GHz) band, respectively. The proposed two designed antennas, with and without shorting pin, are fabricated, and the measured results are in good agreement with the simulated ones. From measured results, a -10 dB-S₁₁ impedance bandwidth (IBW) of 220 MHz (3.38-3.60 GHz) and 460 MHz (3.37-3.83 GHz), a 3-dB ARBW of 200 MHz (3.4-3.6 GHz) and 390 MHz (3.42-3.81 GHz) with respective maximum RG of 2.26 and 2.39 dBic are exhibited by the antennas without and with pin, respectively. The obtained 3-dB ARBWs and -10-dB IBWs make the proposed antennas entirely cover the LTE 42 or LTE 42/43 frequency bands.

Aiming at the problem of large torque ripple caused by large tracking error between actual torque and reference torque in commutation region in direct instantaneous torque control (DITC) algorithm of switched reluctance motor (SRM) based on torque sharing function (TSF), a torque compensation method combining TSF-DITC and model predictive control (MPC) is proposed. Sectors are subdivided in the commutation region according to the rotor position. Different voltage states are selected in different sectors to fully compensate for the tracking error between the actual phase torque and the reference torque distributed by TSF, and then the total torque ripple is greatly reduced. At the same time, the algorithm also effectively reduces the candidate voltage states at the current time and reduces the computational burden. The simulation comparison with TSF-DITC shows that the algorithm (TSF-PDITC) has better steady-state and dynamic performance.

A compact and novel quad element MIMO antenna is presented for ultra-wideband (UWB) applications. The proposed orthogonal MIMO antenna comprises four identical elliptical structure-based tree shape microstrip line fed radiating elements. Radiating elements are placed in orthogonal with each other to obtain low mutual coupling and good diversity characteristics among MIMO elements. The proposed MIMO antenna operates from 4.2 GHz-13.2 GHz with an impedance bandwidth (S₁₁ < -10 dB) of 9 GHz. It is investigated at 5.9 GHz DSRC band for vehicular communication applications and X-band for FSS applications. It exhibits superior characteristics with a peak gain of 6.2 dB at 11.7 GHz and radiation efficiency above 80%. To assess diversity performance of the proposed antenna MIMO performance metrics are investigated. Mean effective gain (MEG) < -3 dB, envelope correlation coefficient (ECC) < 0.05, channel capacity loss (CCL) < 0.4 bits/sec/Hz, diversity gain > 9.99, and multiplexing efficiency > -3 dB. Simulation results and experimentally obtained results are in fine agreement.

An efficient and stability-improved finite-difference time-domain (FDTD) method with auxiliary difference equations (ADE) for cold magnetized plasma is developed in this paper. The two equations of Ampere's law and the auxiliary equation for plasma are unified as a single equation at first. Then the leapfrog difference scheme is applied to it and Faraday's law, respectively. By introducing a mid-term computation into the unified equation, the iterative equations of the ADE-FDTD for plasma are derived. Its stability condition remains the same as that of a vacuum which is analyzed and numerically verified. Numerical experiments show that our proposed method is more efficient than those provided by others but with the same accuracy. Finally, the transmission properties of a magnetized plasmonic slab are investigated. The reflection and transmission coefficients of the right-circularly-polarized (RCP) and left-circularly-polarized (LCP) waves are calculated. The results show that our proposed method can be applied to study these plasma-based structures accurately and efficiently.

Fractal and reconfigurable antennas are the need of modern wireless communication systems that operate under dynamic scenarios catering to the diversified needs of modern wireless applications. In this dissemination, a novel multiband Fractal Reconfigurable Antenna (FRA) has been presented and discussed using two RF PIN diodes as switching elements for electronic reconfiguration. It is analyzed using equivalent circuit concept and investigated in terms of various antenna performance parameters. The proposed FRA can operate in various frequency bands resonating at four different frequencies with switchable bandwidth and gain. The highest gain is observed to be about 8.37 dB at 9.68 GHz while the highest bandwidth is about 540 MHz in the X-band. The simulation and measurement results obtained are found to be in agreement. The multiband characteristics of the proposed FRA make it useful for smart wireless communication applications in the S (2-4 GHz), C (4-8 GHz) and X (8-12 GHz) microwave bands.

This paper proposes an efficient method to simulate the micro-Doppler (MD) frequency of a ballistic warhead by considering a real flight scenario in monostatic and bistatic observations. The radar signal is difficult to obtain by changing the observation angle as the conventional electromagnetic software does obtain the reflected signal for a fixed target, so we transformed the pose of the model engaged in micro-motion in a local coordinates, to the pose on the trajectory, by constructing the transformation matrix. Then we obtained the radar signal by using the point scatterer model and the high frequency estimation method, physical optics, and compared the MD results by using the short-time Fourier transform. In simulations for various observation scenarios, MD signatures were successfully obtained, and scattering characteristics were accurately analyzed.

A defected ground structure (DGS) loaded slotted patch antenna is proposed in this article to achieve multiband response with minimization of cross polar radiations in both the radiation planes. Besides, the antenna in this work achieves reduction in cross polar radiation at all its resonating bands with a simple inset feeding mechanism. Loading of identical U-shaped slots in the patch helps the antenna to achieve dual resonance characteristics and also leads to minimize the orthogonal E-field components. Along with the slotted patch, implementation of DGS results in multiple current paths leading to additional resonances in lower frequency range and also suppresses the strong leakage current in the ground plane. Moreover, three identical slots are loaded at the edges of the ground which balance the strong E-field components in opposite direction improving the reflection coefficient at the different resonating bands. The proposed antenna achieves multi-resonance characteristics operated in 2.44-2.56, 5.45-5.52, 6-6.13, 7.43-8.04, and 8.99-9.17 GHz. Minimization of orthogonal E-field components and suppression of leakage current are responsible for obtaining minimum cross polar radiation from the antenna as -39.08 and -41.01 dB in E- and H-planes, respectively.