This paper proposes a novel source reconstruction method (SRM) based on the convolutional neural network algorithm. The conventional SRM method usually requires the scattered field data oversampled compared to that of target object grids. To achieve higher accuracy, the conventional SRM numerical system is highly singular. To overcome these difficulties, we model the equivalent source reconstruction process using the machine learning. The equivalent sources of the target are constructed by a convolutional neural networks (ConvNets). It allows us to employless scattered field samples or radar cross section (RCS) data. And the ill-conditioned numerical system is effectively avoided. Numerical examples are provided to demonstrate the validity and accuracy of the proposed approach. Comparison with the traditional NN is also benchmarked. We further expand the proposed method into the direction of arrival (DOA) estimation to demonstrate the generality of the proposed procedure.

This paper addresses the problem of target detection in adaptive arrays in situations where only a small number of training samples is available. Within the framework of two-stage adaptive detection paradigm, the paper proposes a class of rapidly adaptive CFAR (Constant False Alarm Rate) detection algorithms, which are referred to as joint loaded persymmetric-Toeplitz adaptive matched filter (JLPT-AMF) detectors. A JLPT-AMF detector combines, using a joint detection rule, individual scalar CFAR decisions from two rapidly adaptive two-stage (TS) detectors: a TS TAMF detector and a TS LPAMF detector. The former is based on a TMI filter, which is an adaptive array filter employing a Toeplitz covariance matrix (CM) estimate inversion. The latter is based on an adaptive LPMI filter that uses diagonally loaded persymmetric CM estimate inversion. The proposed class of adaptive detectors may incorporate any rapidly adaptive TS TAMF and TS LPAMF detectors, which, in turn, may employ any scalar CFAR detection algorithms that satisfy an earlier derived linearity condition. The two-stage adaptive processing structure of the JLPT-AMF detectors ensures the CFAR property independently of the antenna array dimension M, the interference CM, and the number of training samples N_CME to be used for estimating this CM. Moreover, the rapidly adaptive JLPT-AMF detectors exhibit highly reliable detection performances, which are robust to the angular separation between the sources, even when N_CME is about m/2 ~ m, m is the number of interference sources. The robustness is analytically proven and verified with statistical simulations. For several representative scenarios when the interference CM has m dominant eigenvalues, comparative performance analysis for the proposed rapidly adaptive detectors is provided using Monte-Carlo simulations.

In this paper, a novel dual-band scheme is proposed and analyzed for dual-band magnetic resonant wireless power transfer. The scheme consists of a novel resonant coil structure for dual-band resonance and a coupling loop for dual-band impedance matching. Circuit-based analysis and experiments verify that our scheme can achieve dual-band power transfer easily and effectively, with its dual-band reflection coefficient lower than -18 dB and transmission efficiency over 37.21% at a distance of 20 cm at 6.78 MHz and 13.56 MHz.

In this letter, a tuning fork shaped, differential dipole antenna, with two floating reflectors, is presented. The dipole antenna resonates at 1.22 GHz and has a fractional bandwidth (FBW) of 16.39% and a differential impedance of 100 Ω. The proposed antenna is composed of quarter wavelength tuning fork shaped dipole arms in the top layer. To improve robustness, while connecting to the differential circuits, two floating reflectors are used on the bottom layer, beneath the dipole arm. This method helps improving the gain by 7%. A microstrip-to-coplanar strip line (CPS) transition is designed to measure the stand-alone differential antenna. The measured gain and efficiency of the antenna are 2.14 dBi and 84%, respectively, at the resonant frequency. The possible targeted applications are circuits with differential inputs/outputs, like energy harvesting circuits, radio frequency tags, wireless communications and any other wireless sensor network nodes. Details of the design along with simulated and experimental results are presented and discussed.

In this paper a substrate integrated waveguide (SIW) quasi-elliptic filter with a controllable bandwidth is proposed. The quasi-elliptic filter response is caused by the cross coupling technique and a dual-mode resonance cavity. The dual-mode resonance cavity with TE₁₀₁ and TE₁₀₂ modes is used to generate the passband, and the cross coupling provides two signal transmission paths to produce transmission zeros (TZs). The bandwidth of the filter can be controlled by a pair of disturbing metallic via-holes. A quasi-elliptic filter with the center frequency of 11.03 GHz is designed, fabricated and measured. The experiment data agree well with the simulated ones.

Seawater conductivity is an important factor that affects the corrosion electric field of ship.Athree-dimensional boundary element method (3D-BEM) combined with nonlinear polarization curve was employed to investigate the influence of seawater conductivity on the corrosion electrostatic field. Numerical simulation results show that the electric field distribution is only slightly influenced by the conductivity.However, the intensity decreases with the increases of conductivity. The simulation results of the BEM model were compared with the results of the equivalent electric dipole model, and the results obtained by the two methods had high similarity, which demonstrated that the BEM model was effective. The former is a more convenient and concise modeling method that can better reflect the distribution characteristics of ship's corrosion electric field than the electric dipole model.

This paper proposes a compact microstrip bandpass filter (BPF) with high selectivity. A folded stepped-impedance resonator (SIR) of which the high impedance part is realized by a coplanar waveguide on the ground layer is introduced to the filter design for miniaturization. Furthermore, source-load coupling is implemented by extended tapped lines (ETLs). High selectivity with four transmission zeros (TZs) can be achieved. The analysis of the filter is presented based on atransmission line circuit model and even- and odd-mode analysis method. An experimental filter with the size of 0.15λ_g*0.13λ_g (where λ_g is the guide wave-length at the center frequency) is designed to validate our methods.

Performance improvement of couple silver (Ag) - gold (Au) based bimetallic surface plasmon resonance (SPR) sensor using a thin indium phosphide (InP) layer and an air gap layer is presented. Through detailed investigations quantitative insight into the dependence of different performance parameters including sensitivity factor (SF), sensor merit (SM), full width at half maximum (FWHM) and combined sensitivity factor (CSF) on stack structure, thickness and material parameters has been observed. Integration of thin InP layer on the metallic layer and inclusion of the air gap between glass prism and adsorption layer enhance both the sensitivity (70.90˚/RIU) and the CSF (372.8 RIU^-1). Without InP layer the sensitivity is 65.66˚/RIU, and CSF is 178.5 RIU^-1 whereas without the air gap the sensitivity is 66.29˚/RIU, and the CSF is 285.0 RIU^-1. Compared to similar bimetallic SPR sensors that have been reported in recent literatures, sensitivity and overall figure of merit of the proposed sensor are far better. The presented biosensor's capability to detect the variation of 1/1000 of RIU of the sensing medium (corresponding to subtle concentration change of the analyte) has been demonstrated.

Quantitative estimation of both conductivity and permittivity of biological tissues is essential in many biomedical applications, ranging from therapeutic treatments to safety assessment of medical devices and dosimetry. Typically, the electromagnetic field distribution inside the body is predicted based on available ex-vivo measured electrical properties. Unfortunately, these values may be quite different from the ones measured in-vivo and cannot account for the differences among individuals. As a result, their use can introduce significant errors affecting therapeutic treatments and dose estimation. To cope with this problem, in this paper a new approach for estimation of effective electrical properties of human tissues is introduced. The proposed strategy is based on the solution of an inverse scattering problem (by means of a contrast source inversion scheme) and the use of an effective representation of the unknowns based on spatial priors derived by magnetic resonance imaging or computed tomography. The approach is tested in controlled conditions against simulated single frequency data and realistic and anthropomorphic head and neck phantoms. Moreover, the inherent advantages have been assessed in the framework of hyperthermia treatment planning.

The dispersion characteristics of woodpile three-dimensional (3D) function photonic crystals (PCs) composed of plasma and function dielectric elements are theoretically investigated by a modified plane wave expansion method, respectively, and the formulas to obtain the dispersion diagrams are given. Only two cases are considered, which are the presence and absence of the external magnetic field. The external magnetic field is vertical to the wave vector, which means that only the magneto-optic Voiget effect is considered. For the proposed PCs, the function dielectric square columns are inserted into the plasma background with face-centered-tetragonal symmetry according to the woodpile lattices. The relationships between the parameters of such PCs and the features of the photonic band gaps (PBGs) for the extraordinary mode and electromagnetic wave are studied under two different cases. The calculated results show that the dispersion characteristics of the proposed PCs can be tailored by adjusting those parameters. If the extrinsic magnetic field does not exist, larger PBG can be found in the present PCs than 3D dielectric-air PCs, 3D function dielectric PCs and 3D plasma-dielectric PCs with the same lattices. If there is an external magnetic field, the narrower PBG for the extraordinary mode can be obtained than the 3D function dielectric PCs and 3D plasma-dielectric PCs with the same lattices. The computed results also show us a approach to realize the reconfigurable devices based on the PCs.

Aiming at problems that interpolated array has large amount of computation and high sensitivity to transformation angle and interpolated step, a new array extension algorithm which is symmetric extension steering vector is proposed. In this paper, two properties of the conjugate of received data and the source covariance matrix being a real diagonal matrix are exploited to extend the dimensions of the covariance matrix. However, the essence of this extension method is the symmetric extension of the steering vector. The high complexity and degradation of the performance of interpolated array beamforming caused by the sensitivity of angle and interpolated step are improved. Numerical simulations confirm the validity of the proposed algorithm. Compared with existing algorithms, the proposed algorithm is not affected by the angle range of transformation and interpolated step. Besides, the complexity of array extension using this proposed algorithm is much lower than the interpolated transformation method.

An improved matrix synthesis approach for inline filter is presented in this paper. Frequency-variant couplings (FVC) can generate and control multiple finite transmission zeros (TZs). As the resultant network only involves resonators cascaded one by one without any auxiliary elements (such as cross-coupled or extracted-pole structures), this paper provides the best optimizatised synthesis solution in configuration simplicity for narrowband filters based on genetic algorithm (GA) and solvopt optimization method. Compared with the conventional synthesis method for inline topology filters, the method presented in this paper has following advantages: First, it is unnecessary to consider both the couplings and capacitances of a traditional low-pass prototype. Second, there is no need to use similar transformation, and the adjacent FVCs can be implemented. Third, the approach presented can implement more TZs than the previous works. The maximum number of TZs can be as many as the filter order. Two examples with different topologies and specifications are synthesized to show the validation of the method presented in this paper.

The analytical solution of the Biot-Savart equation can be complex in some cases, and its numerical integration is commonly more appropriate. In this paper, it is integrated using the Gauss-Legendre method through 1, 2 and 3-D domains, using first and second-order (curvilinear) isoparametric mapping. In order to verify the gain of accuracy with second-order elements, the results obtained are compared with analytical cases and with the Finite Element Method. Then this paper presents an adaptive method which prots from the accuracy along those elements with higher energy values, by reducing the number of Gauss points along the elements with lower energy. This approach reduces the total number of Gauss points evaluated during the integration process and provides a possibility to choose an interesting trade-off between simulation time and accuracy.

This paper presents a hybrid method consisting of thin wire FDTD method and transmission line (TL) equations to be used for the coupling analysis of multiconductor transmission lines (MTLs) excited by a dipole antenna. In this method, the thin wire FDTD method is used to build the structure of the dipole antenna and obtain the radiation electromagnetic fields surrounding the MTLs, which are introduced into the TL equations as the distribution sources. The TL equations are utilized to model the coupling of the radiation electromagnetic fields to the MTLs, which are discrete by the scheme of the FDTD method to obtain the transient voltage and current responses on the lines and terminal loads. The accuracy and efficiency of this method have been verified by comparing with the commercial simulation software CST via one case. Moreover, the influences of the frequencies and polarization of the dipole antenna and the heights of the MTLs on the coupling of MTLs are analyzed.

This paper proposes to use an Aperiodic Fourier Modal Method (A-FMM) to model an outgoing photonic jet from a dielectric loaded waveguide ended by a tip with a specic shape. The proposed method has several advantages. First of all, the method is fast, which allows to manage optimization investigations. Secondly, the study excitation (and more particularly the impact of plan wave excitation) can be examined precisely. Using our modelling technique, we show, in comparison with an actual optimized elliptical tip, that an optimized rectangular tip improves energy concentration by 8% and reduces the calculation time by a factor of 10. Furthermore, A-FMM allows to show that plane wave excitation modifies the spatial distribution of the jet, especially in the case of TE polarization. This can explain the differences observed, in previous works, where only fundamental mode excitation was used in the modelling. To validate these general results, prototypes have been realized, and measurements in the microwave regime have been compared favorably with simulation results.

Angular misalignment is an issue for many potential applications of wireless power transfer (WPT). It is necessary to keep coupling coefficient, especially the magnetic coupling to be insensitive to angular misalignment. This paper analyzes the coupling between the spiral resonators when one resonator rotates with respect to the other. The quantitative data of magnetic and electric coupling components as well as the total coupling coefficient in angular misalignments are presented. Furthermore, a 3D spiral resonator which is less sensitive to angular misalignment is proposed. The coupling when the 3D spiral rotates is studied and the results of analysis and experiment both show that the proposed 3D spiral resonator can keep coupling coefficient at a certain level under angular misalignment.

Magnetic proximity detection systems (PDSs) used in underground mines occasionally generate false alarms when the miner-wearable component (MWC) is close to nearby conductors such as power cables. This is because the signals from the generators (antennas) of the PDS wirelessly couple to nearby cables, travel along these cables, and then couple back from the cable to a distant MWC to cause a false alarm. In order to manage such a false alarm, it is necessary to understand the basic near-field coupling characteristics from a generator to a long wire. Researchers from the National Institute for Occupational Safety and Health (NIOSH) have developed a method to measure such coupling characteristics for a ferrite-cored antenna to a straight wire. The method is introduced in this paper along with the test results.

An approach to the design and the realization of a broadband multilayer anti-reflection (AR) coating with high transmission is proposed in this study. A binominal multi-section transformer is employed to efficiently determine the thickness and the refractive index of each matching layer, while those layers can be further realized by doping different fractions of subwavelength-size silicon powders (for relatively-high-index layers) or air pores (for relatively-low-index layers) into the low-loss HDPE polymer host. Based on this scheme, we design a ten-layer AR coating for widely used silicon wafer. The designed AR coatings are double-sided integrated with a 375-μm-thick silicon wafer, which can enhance the overall THz transmission to higher than 95.00% from 0.250 THz to 0.919 THz (114.46% fractional bandwidth) for either TE-polarized or TM-polarized THz beam incident from an arbitrary angle below 50˚.

In this paper, an on-chip high integration reconfigurable dipole with band stop filters was demonstrated. This antenna was fabricated on a high resistivity silicon wafer, and several optimized band stop filters were introduced into antenna system to replace conventional inductors and capacitors. The measured results show that the stopband of this filter can meet the requirements of the designed dipole. This method will greatly improve the integration of antenna system. On the basis of structural optimization, the proposed reconfigurable dipole realized two resonant frequencies at 1.33 GHz and 1.65 GHz, and the radiation patterns also showed satisfactory results.

The concept of hidden momentum is reviewed, and the first rigorous derivation from Maxwell's equations is provided for the electromagnetic force on electrically small perfect electric conductors of arbitrary shape in bandlimited but otherwise arbitrarily time-varying fields. It is proven for the Amperian magnetic dipoles of these perfect conductors that a "hidden-momentum" electromagnetic force exists that makes the force on these time varying Amperian magnetic dipoles equal to the force on magnetic-charge magnetic dipoles with the same time varying magnetic dipole moment in the same time varying externally applied fields. The exact Mie solution to the perfectly conducting sphere under plane-wave illumination is used to prove that the expressions for the total and hidden-momentum forces on the arbitrarily shaped electrically small perfect conductors correctly predict the forces on perfectly conducting spheres. Remarkably, it is found that the quadrupolar fields at the surface of the sphere are required to obtain the correct total force on the sphere even though the quadrupolar moments are negligible compared to the dipole moments as the electrical size of the sphere approaches zero.