Scattering of homogeneous plane waves by a Perfect Electric Conductor half-plane in uniform rectilinear motion in a simple lossless medium is investigated using Wiener-Hopf Technique in the context of Hertzian Electrodynamics. The cases of motion being parallel and perpendicular to the plane are tackled separately. Restrictions on incidence angle vs. speed for the realization of scattering phenomena are investigated in each case. Parallel motion mode reveals the possibility of excitation of surface waves upon reflection, which also contribute to edge diffraction mechanism. Numerical results are illustrated and discussed for scattered fields. Comparative theoretical results for the solution of the same problem using Special Relativity Theory are provided and discussed.

A traditional magnetic resonant coupling wireless power transfer (MRC-WPT) system is highly sensitive to the distance between transmitting and receiving coils. The transfer performance deteriorates at short distance due to magnetic over-coupling and magnetic weak-coupling at long distance which also results in the decrease of power. In order to improve the power transfer ability, this paper presents an MRC-WPT system with a novel design of resonant loops. Unlike the conventional system in which the receiving coil is identical with the transmitting coil, the receiving coil in the proposed system is different from the transmitting coil in terms of distance between turns. Theoretical equivalent models are presented to investigate the impact of the mutual inductance on the transfer efficiency. Based on numerical simulation, it is found that relatively more uniform mutual inductance can be obtained with the proposed resonant loops. With the proposed MRC-WPT system, the results show that the power transfer ability at short and long distances is improved. The average transfer efficiency is enhanced about 10% compared with the conventional system. Furthermore, the sensitivity of the proposed MRC-WPT system to lateral and angular misalignments is studied and compared with the conventional system. An experimental prototype of the proposed MRC-WPT system is designed for validation. The results show that the performance of the proposed MRC-WPT system outperforms the conventional system without adding any complicated control circuits.

The loss of magnetic bearing in the process of operation will lead to the temperature rise of the bearing and affect its performance. A permanent magnet is used to provide bias magnetic flux for hybrid magnetic bearing, which can reduce the loss and temperature rise of the magnetic bearing. In this paper, the loss of radial 2-DOF hybrid magnetic bearing (HMB) is analyzed. On this basis, the 3D thermal analysis model of HMB is constructed by using ANSYS Workbench finite element software. The loss is introduced into the temperature field as a heat source, and the temperature distribution of magnetic bearing is calculated. Combined with the results of loss and temperature analysis, the structural parameters were optimized by using genetic particle swarm optimization algorithm (GAPSO). The results show that the loss and temperature rise of the optimized magnetic bearing are significantly reduced.

Synthetic aperture interferometric radiometer (SAIR) is a high-resolution passive imager by sparsely arranging a number of small aperture antennas to synthesize a large aperture. However, the SAIR requires as many receivers as antennas needed, which results in high system complexity and hardware cost and limits the application of the SAIR. Aiming to reduce the system complexity of SAIR, a new passive coding imaging method is proposed in this paper. By using a new aperture coded measurement approach, the proposed method can significantly reduce the number of RF chains while keeping the image fidelity. The effectiveness of the proposed imaging method has been varified by simulations. The results reveal that the proposed method can be an efficient alternative for simplifying the architectures of SAIR.

The aim of this paper was to propose and design a photonic crystal drop filter based on ring resonators and study its properties numerically. This structure is constituted in a two-dimensional square lattice. The resonant wavelengths of the PCRR proposed are λ = 1.553 μm, and the extraction efficiency exceeds 99% with a quality factor of 5177. To study the all-optical OR and XOR logic gate function, we calculated the electric field distribution of the 2D photonic crystal for the 1.553 μm signal light. In order to have a large selectivity of filtering and also of having a fast switching in the field of nonlinearity, we increase the number of ring resonators, and the latter are used for designing all optical logic gates which work using the Kerr effect equal to 10^-6 m²/w.

The paper aims at studying the shielding effectiveness of a closed cylindrical surface simulated by N dielectric coated conducting strips. The far fields of an electric line source in the presence of the simulated surface and in the absence of the surface were calculated, and the ratio between them represents the shielding effectiveness produced around the surface. The solution of the problem was developed based on full wave analysis. In which all fields are represented in terms of infinite series of Mathieu functions. The addition theorem of Mathieu function was employed to facilitate the application of boundary condition. Computer program was developed based on the resulting formulations to produce numerical values. Numerical results are presented for circular and square cross-sectional cylindrical surfaces. Comparison with the published data for the radiation from slotted circular cylinder showed excellent agreement. Other useful results for shielding effectiveness are furnished.

Design of a harmonically tuned RF Power Amplifier (PA) with enhanced efficiency and gain is presented in this letter. It makes use of a tri-band impedance transformer as a two-port output network for facilitating concurrent optimum fundamental and harmonic impedances at the drain terminal. The design is augmented by analytical formulations and analysis to identify the optimal impedance matching scenario at the fundamental, second harmonic, and third harmonic. A thorough analysis reveals that the proposed PA design scheme is very simple while maintaining the performance obtained from the load-pull. A prototype operating at a frequency of 3.5 GHz is developed on RO5880 using 10W GaN HEMT. An excellent agreement between the measured and the EM simulated results validates the proposed design technique.

An antenna array formed by four PIFA elements located very close to each other, with low inter-element matching for MIMO applications is proposed. The antenna array consists of four F-inverted wideband radiators, with a fractional bandwidth around 56%, spaced one to each other by a very short distance (< 0.065 λ0) at a centre frequency of 2.55 GHz. The operational bandwidth goes from 1.88 to 3.15 GHz considering the Sii < -10 dB at each port. Moreover, the coupling among ports reaches values below Sij < -10 dB and getting values less than -30 dB at 1.8 GHz, just by employing an uncomplicated technique implemented by a neutralization line between elements. The antenna array gain goes from 2 dB to 6 dB over the operating bandwidth. Concerning MIMO figures of merit, the radiation pattern of each element is orthogonal to each other. The Envelope Correlation Coefficient is below 0.04 at the designed frequency, reaching a peak around 0.082 at 1.8 GHz, but still achieving the requirement for MIMO operation (less than 0.5). The Total Active Reflection Coefficient (TARC) is almost convergent at the design frequency, showing low dependence on random signals at different elements, and finally, the diversity gain reaches values close to 20 dB, making the array suitable for MIMO access point applications.

High Impedance Textured Substrate is presented for suppression of Surface Waves in Microstrip Antennas. Surface wave propagation limits the radiation efficiency, bandwidth, gain, alters the main beam radiation pattern and increases side lobe levels as well as the back lobes. A novel technique to suppress the surface waves with periodic arrangement of metallic cylindrical pins embedded in the substrate except the area underneath the radiating microstrip patch is presented here. Two structures with solid as well as hollow cylindrical pins are analysed with Spectral Domain Analysis. The textured pin bed structure creates negative permittivity and high capacitive impedance and thus suppresses the propagation of TM-surface waves. The gain of 11.83 dB with an enhancement of 6dB over normal microstrip patch antenna is achieved. Further an increase of 1.61 dB gain with 12.27% improvement in radiation bandwidth is observed in the antenna structure with hollow cylindrical pins as compared to that of solid cylindrical pins. A uniform gain of more than 11 dB is achieved with a percentage bandwidth of 17.43%.

In this paper, a dual-band Multiple Input Multiple Output (MIMO) antenna for fifth-generation (5G) band (3.3-3.6 GHz and 4.8-5.0 GHz) is presented. The proposed MIMO antenna fed by coplanar waveguide (CPW) contains two symmetric antenna elements with two inverted L-shaped stubs. High isolation is successfully acquired by adopting a double-Y-shaped stub and partial ground plane. To obtain compactness, the antenna printed on an FR4 substrate has two triangle corners cut off. To study the performance, the antenna is simulated by Ansoft HFSS 13.0, and then fabricated and tested. The measurement results demonstrate that the antenna has achieved impedance bandwidths (S₁₁ < -10 dB) of 790 MHz (3.08-3.87 GHz) and 880 MHz (4.7-5.58 GHz) with fractional bandwidths of 22.7% and 15.8% respectively, which covers 3.45/4.9 GHz 5G bands. Meanwhile, the measurement results exhibit an enhanced isolation more than 20 dB, a low envelope correlation coefficient (ECC) below 0.001, an average gain better than 2 dB and a stable radiation pattern within operation bands. In addition, the parameters including efficiency, DG, CCL, MEG and TARC are also analysed. The simulated and measured results indicate that the proposed MIMO antenna can be applied to 5G communication system.

A dual-band antenna operating in dual bands is presented. The antenna is composed of two substrate layers covered with three printed patch layers. The top layer is an electrically small ring; the middle consists of four spiral resonators (SRs); and the bottom is a split-ring resonator (SRR). Inductive couplings between layers change the radiation Q factor of the original ring antenna and promote resonating modes in UHF and S bands. Besides, the input matching property is also improved. The measured return loss agrees well with the calculated results, and the radiation patterns are also presented. From experiments it is found that the proposed antenna is electrically small at operation dual-bands.

For a radiating structure such as dipole/patch array mounted on an aerospace platform, the radiation mode radar cross section (RCS) plays a significant role compared to the structural mode RCS. Thus the estimation and control of array RCS without degrading its radiating characteristics poses a challenge for an antenna engineer. In this paper, a novel design of a low profile 4-element patch array with hybrid HIS-based ground plane is presented to demonstrate both in-band and out-of-band structural RCS reductions. A significant broadband reduction in structural RCS has been achieved from 1 GHz to 80 GHz. The radiation mode RCS of the patch array is computed and controlled through optimized design parameters without degrading the radiation characteristics. The computed array RCS shows that even radiation mode RCS can be reduced except in operating frequency range.

A triple-section arm structure is proposed for designing a planar spiral antenna. All three sections are designed by combining logarithmic, rooted, and sine equations. The slowly outstretched and contractive structure is innovatively realized. According to the radiation characteristics of the spiral antenna, each section corresponds to different in-band enhancement effects. Numerical simulation in the frequency domain and experiments using two different baluns are carried out. The results show that the novel spiral topology could simultaneously achieve improved axial ratio, low cross-polarized gain, and excellent impedance matching throughout the whole band. The axial ratio is reduced by 1.5 dB at mid frequencies and more at low frequencies, comparing the proposed arm with a sinusoid-added equiangular spiral arm. Without applying the resistive loading method, a lower cut-off frequency of 750 MHz is still realized both in impedance bandwidth and axial ratio bandwidth. The low cut-off frequency of the proposed arm is 30.2% lower than the conventional Equiangular spiral arm. Besides, the polarization isolation is significantly improved, especially at low frequencies. Therefore, the proposed miniaturized spiral arm structure could be a competitive form for designing spiral antennas.

The design of a compact stubbed microstrip balun with very wide range higher order harmonic suppression, is presented based on multiple open stub units, for which advantages are twofold, compared to single and double open-stub based designs. First, the high degree of size and harmonic reduction is achieved within the realizable impedance values. Second, the achieved bandwidths are fairly large (close to those of conventional balun) for a given set of electrical lengths. Unlike other methods, here, predetermined bandwidth analysis is provided for various levels of size and harmonic reduction. A prototype balun, having 75% size reduction and simultaneous wide higher order harmonic suppression extended up to 12f₀, while maintaining good input matching, amplitude and phase balance bandwidths, is fabricated for validation.

This article deals with the generalized procedure of designing and optimizing multi-ring radial and thrust permanent magnet bearings (PMBs) with an axial air gap for maximum force and stiffness per volume of the magnet. Initially, the procedure of determining optimized design variables in both the configurations is presented using the MATLAB codes written for solving the three dimensional (3D) equations of force and stiffness in PMB having `n' number of rings on the stator and rotor. The maximized results of the forces in both radial and thrust multi-ring PMBs are validated with the values obtained using finite element analysis (FEA). Then, the correlation between the optimized parameters and the air gap is obtained, and curve fit equations for the same are proposed in terms of stator outer diameter. Further, curve fit equations establishing the relationship between the maximized bearing features, and the aspect ratio (L/D4) of the bearing are expressed for different values of air gap in both the radial and thrust bearings. Finally, the generalized method of designing and optimizing the multi-ring PMB is demonstrated with a specific application. A designer can use the presented curve fit equations for optimizing design variables and calculating maximized bearing features in multi-ring radial and thrust PMBs easily just by knowing the bearing features for a single ring pair.

In this research work a compact patch antenna which is reconfigurable for frequency is presented. Frequency reconfigurability is achieved by the use of two PIN diodes. Antenna operates over four frequencies, i.e., for WiMax (4.94 GHz), WLAN (5.35), and C-Band (6.25 and 6.83 GHz) applications. The overall dimension of antenna is 25×25 mm², and an FR-4 substrate having dielectric constant of 4.4 and thickness 1.6 mm is used to fabricate the prototype of the proposed antenna. Different resonant frequencies are obtained by cutting a ∏-slot and a U-slot in radiating patch and by modifying ground slot with a modified slotted structure. One diode is used in ground, and another PIN diode is used on the patch at an appropriate position. Maximum gain of 3.91 dBi and stable radiation characteristics and VSWR < 2 are obtained at the operating bands in simulation and measurement. The antenna elicits its novelty through compactness, portability for communication devices through combination of only two PIN diode switching in cellphones, tablets PCs, and other satellite communication devices operating in C-band as per FCC standard. A prototype of antenna is fabricated, and the measured and simulated parameters are in good agreement.

In coaxial magnetic gear (CMG), magnetic modul ation ring is composed of a modulator and a connecting bridge. The torque performance of the magnetic gear are affected by the different structures of the magnetic modulation ring. In this paper, fifteen different kinds of magnetic modulation rings with different structures are proposed; they consist of three different shapes of modulators and five different locations of connection bridges. By using the two-dimensional finite element method (FEM), the magnetic flux density, magnetic line distribution, static torque, and steady-state torque of the CMG with different structures of magnetic modulation ring are analyzed. The results show that the innermost bridge has the least effect on the torque and torque ripple of the CMG, while the outermost bridge has the opposite effect. The torque capacity of the circular modulator and arc modulator is higher than that of the square modulator, and the circular modulator helps to reduce the inner torque ripple, while the square modulator helps to reduce the outer torque ripple. This paper can provide some references for the design of the magnetic modulation ring.

A planar I-shaped folded-patch antenna with a footprint of 21 mm x 21 mm x 1.6 mm is designed for compact UHF RFID tags to cohere on metal. The antenna consists of three parts: a square ground plane, an I-shaped patch and a ring resonator. The I-shaped patch is interconnected to the ground plane through a narrow shorting stub, and the microstrip feed line is inserted into the patch to reduce the input impedance of the patch. Extra capacitance and inductance introduced by the ring resonator can lower the tag's resonant frequency down to the expected UHF RFID band. The proposed antenna is manufactured, and there is excellent consistency between simulation and measurement results. The proposed tag antenna achieves a far read distance up to 6.3 m on metal (with 4 W equivalent isotropic radiated power) at resonant frequency of 920 MHz.

Magnetic micro-robots are used widely in a narrow space, such as internal inspections and desilting of slender pipelines, minimal- or non-invasive diagnoses and treatments of various human diseases in blood vessels, and micro-manipulations, micro-sensing fields. Magnetic micro-robots are usually driven by several electromagnetic coils. It is essential to understand the magnetic field and magnetic forces acting on micro-robots to drive the magnetic micro-robots more effectively. In this paper, the finite element method is applied to simulate the magnetic field generated by a coil assembly. Moreover, a three-dimensional magnetic force simulation is also performed to reveal the magnetic forces acting on a cylindrical magnetic micro-robot. Experimental measurements validate the simulated results. A Hall sensor is used to measure the magnetic field along the coil assembly's axial and radial direction. The micro-robot is glued to a connecting rod, fixing a force sensor to measure the magnetic forces acting on it. The measured results are in good accordance with the simulated ones, which prove the validity of the simulation. The results from this study show potential to provide a reference to magnetic micro-robot applications.

Compressed sensing (CS) imaging radar can obtain higher resolution than the traditional synthetic aperture radar (SAR) with less data, which makes it important for military and civilian applications. However, noise, especially active noise jamming will degrade its performance. This paper describes the signal model of the CS imaging radar under noise jamming. Through theoretical analysis and simulation experiments, the influences of different jamming patterns, jamming parameters and reconstruction algorithms on the performance of CS imaging are compared. It can provide reference for the research of anti-jamming technology of CS imaging radar.