In general, the problem of the excitation (radiation, scattering) of electromagnetic fields by a system of finite-dimensional material objects in arbitrary electrodynamic volumes is formulated. On the basis of the impedance concept, the problem is reduced to solving two-dimensional integral equations for electric surface currents on material objects. A physically correct transition from the obtained integral equations to a system of one-dimensional equations for currents on electrically thin impedance vibrators (monopoles) with electrophysical and geometric parameters that can be irregular along their length is made. As an example, a system of two monopoles with a variable surface impedance located in a rectangular waveguide is considered. The problem was solved by the generalized method of induced electromotive forces (EMF). A distinctive feature of this method is that the current distribution functions found by the asymptotic averaging method are used to solve integral equations for currents. The numerical and experimental results concerning electrodynamic characteristics of the structure under consideration are presented.

The present paper develops an application of the bandpass (BP) negative group delay (NGD) circuit for the design of an independent frequency phase shifter (PS). The design principle of the innovative PS is constituted by an inductor-capacitor-inductor (LCL) T-shape passive cell in cascade with RLC-network series-based BP NGD circuits. The S-matrix analytical model of the LCL-NGD PS is established in function of the circuit elements. Then, the design equations of the PS elements in the function of the expected PS value and center frequency are formulated. The NGD PS topology is validated with a comparison between the calculated and simulated results of phase, transmission coefficient, and reflection coefficients. As expected, a very good correlation between the analytical model and the simulation is confirmed by the obtained results. It is found that the LCL-NGD PS presents an outstandingly flat phase shift of -120°±5° with 1.2 GHz center frequency. The LCL-NGD PS operates with about 18% relative bandwidth. The PS reflection coefficient presents a magnitude flatness around -3±1.5 dB. Moreover, the reflection coefficient is kept better than -15 dB. The sensitivity of the LCL-NGD PS performances over the NGD circuit element ±5% relative variation is studied. It is found how the PS value and center frequencychange with the R, L, and C components of the NGD circuit.

In a wireless magnetic induction communication system, the magnetic field distribution of the current-carrying coil affects the communication effect between the communication transceiver and receiver. In the study of magnetic field distribution, it was found that magnetic induction intensity and magnetic flux were important parameters to measure the effectiveness of communication. Aiming at the circular coils with rectangular cross-section of any turn numbers, this paper proposed an improved algorithm to calculate the magnetic induction intensity at any spatial position based on Biot-Savart law. At the same time, the calculation formula of the magnetic flux at the receiving point was also given. The coils were modeled and simulated with COMSOL software. The correctness of the improved algorithm was verified and compared with the traditional formula and simulation results, especially in the near field, which provided an important theoretical support for the further study of mutual inductance in the wireless magnetic induction communication system.

This paper is the continuation and development of the discussion started in our previous work with the same title. For the first time, eigen waves of the plane boundary separating vacuum and an artificial plasma-like medium are considered in reasonably substantiated way and in a sufficiently extensive and profound volume. The possibility of extending the results obtained for a plane boundary to the case of a weakly profiled periodically uneven boundary is shown. This paper demonstrates the potential and urge to use the analytical results in the studies of the resonant transformation of the field of a plane, density modulated electron beam flying over a periodically uneven boundary of a natural or artificial medium in the field of bulk outgoing waves.

This article presents a compact, single feed dual-band dual-polarized (DBDP) microstrip antenna. The proposed design involves an inverted Y-shaped radiating patch and a rectangular open-loop positioned near its right corner that creates mutual coupling to attain wideband circular polarization (CP). To achieve enhanced axial ratio bandwidth (ARBW), a semi-rectangular ground plane with two asymmetric truncated L-shaped slots has been used. An L-shaped slotted quarter wave microstrip line feed is used here for broader ARBW and proper impedance matching. The measured dual impedance bandwidths (IBW) in the range 5.85-6.52 GHz (centre resonance frequency f_rc1 = 6.19 GHz, 10.66%) in lower frequency region and 7.25-13.64 GHz (f_rc2 = 10.445 GHz, 61.18% bandwidth) in higher frequency region. The two ARBW bands span over 7.22-10.99 GHz (f_c1 = 9.105 GHz, 41.41%) and 11.67 GHz-12.25 GHz (f_c2 = 11.96 GHz, 4.85%). The measured peak gains between 3.20 and 4.96 dBi over the entire IBW range makes the LP and CP bands suitable for ITS (5.9 GHz), U-NII-5 of 6 GHz band, some C-band, ITU-8 GHz, some X-band, and Ku-band applications.

In this paper, we propose a fine scale partially coherent patch model (FPCP) for GNSS-R land applications for soil moisture retrieval. The land surface is divided into coherent planar patches on which microwave roughness is superimposed. The scattered waves of the coherent patch are decomposed into the coherent specular reflection and diffuse incoherent scattering. A fine scale of 2 meter patch size is chosen for the coherent patch to be applicable to complex terrain with large varieties of topographical elevations and with small to large topographical slopes. The summation of scattered fields over patches is carried out using physical optics. The phase term of the scattered wave of each patch is kept so that correlation scattering effects among patches are accounted for. Results are illustrated for power ratio for areas near the specular point and areas far away from the specular point. Comparisons are made with the radiative transfer geometric optics model. DDM simulations are performed with good agreement with CYGNSS data.

This paper proposes a new integration of compact ultra-wideband (UWB) slotted monopole antenna with a diplexer and rectifier for simultaneous energy harvesting and data communication applications. The antenna is composed of four symmetrical circularly slotted patches, a feed line, and a ground plane. A slotline open loop resonator based diplexer is implemented to separate the required signal from the antenna without extra matching circuit. A microwave rectifier based on the voltage doubler topology is designed for RF energy harvesting. The prototypes of the proposed antenna, diplexer, and rectifier are fabricated, measured, and compared with the simulation results. The measurement results show that the fractional impedance bandwidth of proposed UWB antenna reaches 149.7% (2.1GHz-14.6 GHz); the diplexer minimum insertion losses (|S₂₁|, |S₃₁|) are 1.37 dB and 1.42 dB at passband frequencies; the output isolation (|S₂₃|) is better than 30 dB from 1 GHz to 5 GHz; and the peak RF-DC conversion efficiency of the rectifier is 32.8% at an input power of -5 dBm. The overall performance of the antenna with a diplexer and rectifier is also studied, and it is found that the proposed new configuration is suitable for simultaneous microwave energy harvesting and data communication applications.

A conductor backed CPW-based S-band filter using Multiple Ring Resonators (MRR) is presented. The resonator is coupled with the feed line through inter-digital coupling. Square resonator structure joined with inter-digital coupling on both sides on conductor plane and multiple ring resonators implemented with equal spacing at the ground plane forms a conductor backed CPW filter model. Adjusting the size and gap factor of MRR, the wide tuning ranges of desired frequencies are achieved. The filter has an outstanding bandwidth range from (2-4) GHz which fits for Satellite S-Band applications. The S-Band has low insertion loss (-0.95 dB), lower return loss (-35 dB), wide bandwidth (fractional bandwidth 66.6%) at the center frequency 3 GHz are obtained. The size of the filter performance characteristics are investigated and compared with measured results. The complete measurement of filter is (39×7.2×1.6) mm. The measured values of S₁₁ and S₂₁ are about -25 dB and -1.92 dB respectively.

Convex lenses can be used in adjuvant with microwave sources to produce appropriate focus spots for breast cancer hyperthermia therapy. A preclinical system was assessed using a horn antenna together with a convex lens. The horn antenna was built to accommodate the lens size so as to minimize wave spillover. Here, a modified hyperthermia system was tested on a hemisphere phantom of scattered fibro glandular breast tissue with cancer stages I & II. The focus spots were at different locations and depths (up to 2.7 cm) under the skin layer. Transmission and reflection coefficients at the air-breast phantom interface were calculated to determine the best operating frequency (2.45 GHz) for efficient power absorption. Based on these computations, an external dielectric matched layer was added onto the skin of the breast phantom to decrease reflection that would occur between water and skin. This arrangement increased wave transmission inside the breast without increasing applicator input feed. The system could heat regions of tumor at various locations independently using only one applicator. The whole system was fabricated, and measurements were taken to validate the simulated and analytical results.

Knowing the state-of-health (SOH) of equipment, device or component is very essential for the secure and dependable operation of a system. Electrolytic capacitors are undoubtedly one of the essential components of power supply modules used in aerial and underwater vehicles, and every equipment requires a conversion of voltage from one level to another. This has encouraged research into the components of the power supply used in such systems of which electrolytic capacitor is of interest in this study. In this paper, we explore a new approach to implementing prognostics and health management (PHM) for electrolytic capacitors and propose a method of estimating the SOH leading to the prediction of the remaining useful life (RUL). This is accomplished by using a bidirectional long short-term memory (BLSTM) network to capture the degradation trends. We demonstrate the power and leverage that this method brings to bear in encoding time-domain dependencies in accurately estimating the SOH bereft of state models as employed in traditional methods. We validate the proposed approach using capacitor data recorded at different electrical over-stress accelerated aging conditions. The proposed method surpasses other existing methods in RUL prediction as indicated by the error and relative accuracy.

In this paper, high efficiency multi-functional all-optical logic gates based on a metal-insulator-metal (MIM) plasmonic waveguide structure with Kerr-type nonlinear nano-ring resonators are proposed. The proposed structure consists of three straight input ports, eight nano-ring resonators filled with the Kerr-type nonlinear medium, and one straight output port. By fixing the input signal power and properly changing the control power, it can be used to design high efficiency multi-functional all-optical logic gates. The numerical results show that the proposed Kerr-type nonlinear plasmonic waveguide structures could really function as all-optical XOR/NXOR, AND/NAND, and OR/NOR logic gates in the optical communication spectral region. The transmission efficiency of the high logic state is higher than 95%, and that of the low logic state is about 0% at the wavelength 1310nm. The performance of the proposed logic gates was analyzed and simulated by the finite element method (FEM).

A novel wideband beam reconfigurable magneto-electric dipole patch antenna is presented in this paper. The proposed antenna consists of two H-shaped patches, two folded patches, an E-shaped feeding structure, a side-slotted ground, and a large reflective ground. Two H-shaped patches are horizontally placed on both sides of the feed structure, and two folded patches are assembled vertically to the upper ground, which are designed as the magneto-electric dipole structure. Two symmetrically sided slots are etched on the upper ground to reduce the profile, and an E-shaped strip is employed in the feeding structure to broaden the bandwidth. To suppress the backward radiation, a lower ground with large size is designed as a reflector. Four binary switches are symmetrically integrated on the stubs of H-shaped patches. By switching them ON or OFF simultaneously, the current distribution is changed to achieve beam reconfigurability. Finally, a set of antenna prototype with four configurations is fabricated and measured. The measured results show that maximum impedance bandwidth achieves up to 77.8% at 2.7 GHz from 2.0 GHz to 4.1 GHz. At 2.7 GHz, the measured peak gains are 8.4 dBi, 9.3 dBi, 8.1 dBi, and 8.7 dBi, where the beams point to -21˚, 0˚, 21˚, and 34˚, respectively in E-plane.

For replication concerns, this paper describes the work of the LAPLACE Electromagnetism Research Group to build NASA-like cavities in order to exploit the same electromagnetic configuration: the same resonant mode. These cavities are then implemented in our straightforward EMDrive experimental setup with a 0.1 mN sensitivity. Force measurement protocol is presented and discussed while more than 150 W of RF power is injected into the cavities. Results are compared to the NASA stated thrust to power ratio of 1.2±0.1 mN/kW.

This work presents an efficient method that allows to accurately calculate the time-harmonic vertical magnetic field generated at the center of a large current-carrying coil of wire positioned above a layered ground. The method consists of evaluating the integral representation for the vertical magnetic field by using a hybrid procedure. At first, the direct and ideal reflected fields are extracted from the total magnetic field and expressed in explicit form. Then, the non-analytic part of the integrand of the remaining contribution is replaced with a sum of partial fractions, obtained by using a rational function fitting algorithm. Finally, the resulting sum of integrals is analytically evaluated and turned into a sum of modified Bessel functions of the second kind. The obtained expression for the magnetic field is then used to evaluate the voltage induced in a small receiving loop co-axial with the transmitting loop.

In order to shorten design optimization cycle and reduce the influence of low-order harmonic for multi-phase induction motor, two kinds of five-phase motors - using either a star or pentacle-star hybrid winding - are proposed based on the Y160L-4 three-phase induction motor, which keep the structure size of the stator and rotor and rated power constant, redesign the winding, and adjust the match parameters of the stator and rotor slots. Based on the Fourier series expansion method, the time-space harmonic magnetomotive force (MMF) analytic function of pentacle-star winding was given based on star winding MMF. According to the analysis for the MMF table of three kinds of induction motors, pentacle-star winding with 19th-order harmonic has a better performance than star-winding with 9th-order harmonic and three-phase delta winding with 5th-order harmonic. Further analysis suggests that the harmonic torque generated by the harmonic MMF can be used to improve the electromagnetic torque, and the effective torque characteristics of the three forms of induction motors are given. Two kinds of five-phase motors with different winding configurations can be realized based on the three-phase motor, and some simulated and experimental resluts show that the method is feasible, which provids significant value in engineering applications.

A method is given for evaluating electromagnetic scattering by an irregular surface with spatially-varying impedance. This uses an operator expansion with respect to impedance variation and allows examination of its effects and the resulting modification of the field scattered by the rough surface. For a fixed rough surface and randomly varying impedance, expressions are derived for the scattered field itself, and for the coherent field with respect to impedance variation for both flat and rough surfaces in the form of effective impedance conditions.

A dual-mode dual-band bandpass filter with high cutoff rejection using asymmetrical transmission zeros technique is presented here. Two dual-mode filters are combined to form a dual-band filter by sharing the input and output coupled-feed line, which is more flexibility-designed and maintains a small circuit size. Controllable asymmetrical transmission zeros (TZs) at lower- and upper-sideband locations of dual-band filters are designed to achieve the high-selectivity dual-mode dual-band bandpass filter. Unwanted signals are suppressed by the places of the TZs between the first and second passband, which give much-improved signal selectivity for the dual-band bandpass filter. The two passbands are centered at 1.8 and 2.4 GHz, respectively. The first and second passbands' insertion losses are only 0.9 dB and 1.1 dB, and the measured return losses are better than 20 dB. Three transmission zeros are located between both passbands, which achieve the rejection levels about 40 dB attenuations from 1.9 to 2.3 GHz.

In this work, a numerical quasi-static approach is proposed to efficiently analyze symmetrical shielded broadside-coupled microstrip line (SBCML) structures. Based on the modified least squares boundary residual method combined with a variational technique, this approach allows accurate computation of the electrical/geometrical parameters of different SBCML configurations. The errors for the quasi-TEM electrical parameters range are less than 4%. The proposed technique was demonstrated through successful comparison with data from published works and results obtained from commercial EM simulators like CST-EMS and COMSOL.

To meet the growing requirements of Standard Positioning Services (SPS) and Precision Services (PS), more and more GNSS systems operating at conventional GPS frequencies and higher frequency bands are launched. The Indian NavIC system is one of such systems transmitting navigational signals at S1 (2492.028 MHz) and L5 (1176.45 MHz) frequencies. For GPS at L-band frequencies, comprehensive research work has been conducted to analyze the ionospheric delay to estimate precise user position, although very little research work is available in the public domain at the navigational S-band level. The NavIC program provides opportunities to explore the ionospheric delay effect on S-band navigational signals. The precise position determination demands accurate estimation of the vertical ionospheric delay which is generally obtained using Vertical Electron Content (VTEC) of the ionosphere. The VTEC can be obtained by multiplying a mapping function to the Slant Total Electron Content (STEC). Conventionally a thin shell (also known as a single shell) model is used to map STEC to VTEC, but it introduces error at low elevation angles. This error is significant for the NavIC receivers, located in the northern part of India, as they observe elevation angles below 50° for most of the time, and thus there is a need to investigate the suitability of the mapping function model for the NavIC system. As the ionospheric shell height modifies the mapping function and results in a change in VTEC, the height and thickness of the thick shell have been investigated based on the ionospheric data taken from IRI 2016 and were estimated as 300 km and 250 km, respectively. In the present work, the thick shell model has been compared to thin shell model mapping functions to improve the accuracy of VTEC estimation at the low elevation. The reduction in vertical delay using the thick shell mapping function at low elevation indicates its suitability for the locations like Dehradun, India, which lies in the mid-latitude region. Furthermore, the temporal variability of vertical delay at S and L band frequencies has also been investigated to understand the diurnal and seasonal characteristics of ionospheric vertical delay over a period of 12 months to cover all the seasons during the year 2017-18. The vertical delay at the S-band frequency was found to be less than that at the L-band frequency and is almost constant over a month. This finding will be beneficial for single-frequency users and could be used to develop the Grid Ionospheric Vertical Delay (GIVD) map for the NavIC system to enhance positional accuracy.

A novel and efficient higher order convolutional perfectly matched layer (CPML) method is put forward and also applied to cut off the finite-difference time-domain (FDTD) computational domain full of the unmagnetized plasma. A Drude model can be used to represent the unmagnetized plasma, and the plasma can be solved by using the trapezoidal recursive convolution (TRC) method. In order to verify the validity of the presented method, a numerical example in three-dimensional computational domain is provided. The numerical example results show that the proposed formulations have better absorbing performance than the first-order CPML in terms of attenuating low-frequency and evanescent waves. Besides, by using the proposed method, computational time and memory can be reduced compared to the second order PML implemented by using the auxiliary differential equation (ADE) method.