The composite scattering of an electrically large target above nonlinear sea surface is analyzed based on the reciprocity theorem. The two-dimensional nonlinear sea surface is simulated with the Fast Fourier transform (FFT), with which the phase modified two-scale method is utilized to calculate the scattering field of the wind-driven sea surface. The electromagnetic currents of the sea surface, which are excited with plane wave, are calculated with the iterated Kirchhoff approximation (KA).The coupling scattering between the target and the sea surface, which includes the complex scattering matrix of composite scattering, is ingeniously reduced to the integrals involving the target scattering and high order currents of sea surface. A sensitivity analysis is performed for the dependency of the coupling scattering on the target features. The relationship of the full composite scattering model with the sea state is examined, which provides theoretical basis for the target recognition.

An efficient method based on the recursive fast Fourier transform (FFT) to incorporate both the intra-band and inter-band conductivity terms of graphene into the finite-difference time-domain (FDTD) method is proposed. As it only requires numerical values of the conductivity, it not only does not enforce any restrictions on the conductivity models, but also can directly take into account material properties obtained from measurement. It reduces the total computational cost from O(N²) to O(Nlog²N) where N is the length of the unknown. The FDTD method is also modified and proven to retain the stability condition of the standard FDTD method.

A miniaturized frequency selective surface (MFSS) that has very stable performance is designed based on the stepped-impedance element (SIE) structure. Significant couplings can be introduced by overlapping one metallic layer above the SIE structure. The large overlapping areas between the two metallic layers is beneficial to further miniaturizing the element size. Therefore, the physical size of the MFSS unit cell can be reduced to 0.054λX0.054λ. In addition, the MFSS is proved to excellent stability towards incident angles (up to 75^o) and polarizations. A careful equivalent circuit model is presented to explain the physical principle of the proposed design. Finally, a prototype is fabricated and tested, and the simulation results are in agreement with the experimental observations.

In this article, a novel design of butterfly-shaped compact and small size microstrip antenna is proposed. The radiating structure consists of four circular discs in coalesced form and fed with coaxial probe. The initial antenna resonates at 9.64 GHz with impedance bandwidth of 11.41%. The resonance frequency is further reduced to 8.12 GHz with bandwidth 10.10%, when a rectangular slot is incorporated in the initial patch. Finally, two parallel slots are embedded in the initial patch which improves the antenna bandwidth up to 21.50% (6.02-7.47 GHz). The gain and efficiency of this antenna are above 8.80 dBi and 90% respectively across the entire operating band. Radiation pattern is calculated at lower end (6.02 GHz), upper end (7.47 GHz) and centre frequency (6.75 GHz) of operating band. The proposed antenna is fabricated, and measured results are validated with the simulated ones.

In this article, a novel phase mode analysis for a circular antenna array is discussed. This proposition experiments on the synthesis of Dolph- Chebyshev pattern for circular geometry employing directional element 1+cos(φ). Here, for pattern synthesis a modied uniform sampling method is proposed, and for investigation of continuous current excitation in a circular array, a Fourier phase-mode approach is proposed. The synthesis process permits generation of complex weights for each element to produce the Chebyshev pattern with a desired beamwidth or Side Lobe Level (SLL). The radius is a key factor for a circular geometry and also decides the pattern synthesis, which is determined by using the phase mode concept. Also, this article contributes to the formulation of a mathematical relationship between the number of phase modes (P) and number of antenna elements in the array (N) such as N = 2(P-1).

This article proposes a computational scheme for a combined field integral equation to compute electromagnetic scattering, which is Reduced order Fitting Green's function's Gradient and Fitting Green's function with Fast Fourier Transform (ROF). This new scheme can greatly reduce computation time compared to integral equation Fast Fourier Transform (IE), as well as Fitting Green's function's Gradient and Fitting Green's function with Fast Fourier Transform (FGG). Firstly, based on the property of Green's functions' integral under special condition, real-coefficient fitting method is utilized to replace the original complex values expression of combination coefficients with the real values. Secondly, a cross-shaped grid named as reduced order grid is presented to reduce computation time for modified near-field coupling impedance. Thirdly, by combining real-coefficient fitting method and reduced order grid, a new scheme of ROF is achieved. Finally, some examples verify ROF, which has advantages, such as higher efficiency than that of IE based on original grid and FGG based on cross-shaped grid, being not sensitive to grid spacing, and keeping the same precision as that of IE based on original grid.

Most of the materials have nearly constant electromagnetic characteristics at low frequencies. Nonetheless, biological tissues are not the same; they are highly dispersive, even at low frequencies. Cable theory is the most famous method for analyzing nerves though a common mistake when studying the model is to consider a constant parameter versus frequency. This issue is discussed in the present article, and the analysis of how to model the dispersion in the cable model is proposed and explained. The proposed dispersive model can predict the behavior of excitable cells versus stimulations with single frequency or wide band signals. In this article, the nondestructive external stimulation by a coil is modeled and computed by finite difference method to survey the dispersion impact. Also, 5% to 80% difference is shown between the results of dispersive and nondispersive models in the 5 Hz to 4 kHz investigation. The disagreement expresses the dispersion notability. The proposed dispersive method assists in accurate device design and signal form optimization. Noise analysis is also achieved by this model, unlike the conventional models, which is essential in the analysis of single neurons or central nervous system, EEG and MEG records.

Antenna pattern measurement is an essential step in antenna qualification which should be done in anechoic chambers. The common method for anechoic chamber construction is to cover all inside walls by the electromagnetic absorbers. In this paper, a new method is presented to design a fully metallic chamber by controlling the electromagnetic inside the chamber and guiding them to a piece of absorber. Therefore, a desirable quiet zone is formed inside the chamber while a great reduction of absorber usage is achieved. The proposed chamber is analyzed using ray tracing method, and its performance is evaluated by simulation that shows the practicality of the proposed chamber.

A novel circularly polarised antenna with wide 3 dB axial-ratio beamwidth (ARBW) and half power beamwidth (HPBW) is proposed in this letter. By using two pairs of tilted dipoles, the ARBW of the antenna is significantly enhanced to about 160° and 162° in the XZ- and YZ-planes, respectively. Meanwhile, its HPBW is also broadened to above 116° in the dual planes. A prototype is manufactured and measured to validate the method. The measured results show that |S₁₁|<-10 dB reaches about 38.8% (1.37 GHz-2.03 GHz), and the AR at broadside bandwidth is 14% (1.51 GHz-1.74 GHz). The gain of the antenna also keeps above 4.19 dBic. Meanwhile, acceptable agreements can be obtained between the simulated and measured results. As such, the proposed CP antenna with wide beamwidth can be used in various navigation systems.

In this paper, a novel planar monopole ultra-wideband (UWB) antenna with quad notched bands is investigated. The proposed antenna is composed of a circular-shaped radiating element, a 50 Ω microstrip feed line, a quad-mode stepped impedance resonator (SIR), and a partially truncated ground plane. By coupling a quad-mode SIR with an additional outer line beside the microstrip feedline, band-rejected filtering properties around C-band (5.2/5.8 GHz) WLAN bands, and X-band (8.5/10.5 GHz) satellite communication bands are generated. The measurement of voltage standing wave ratio (VSWR) is in agreement with simulation. The results show that the proposed antenna not only retains an ultrawide bandwidth but also owns quad band-rejections capability. The UWB antenna demonstrates omnidirectional radiation patterns across nearly the whole operating bandwidth that is suitable for UWB applications.

The principles of ideal wideband RAAs are determined through the idea of distortion-less radiation of a modulated pulse. Two conditions for the cells and one condition for the location of the feed are obtained. The conditions are discussed and clarified by some examples. Each cell requires its own phase at center frequency and its own phase derivative in the desired bandwidth. Some relations are obtained and discussed for the range of required phase derivative of the cells.

In this letter, a compact second-order mixed coupling bandpass filter (BPF) with one controllable transmission zero (TZ) near the passband edge is presented using multilayer substrate integrated waveguide (SIW). Two arranged circular SIW resonators can be vertically coupled via the circular apertures etched on the middle metal layer while preserving a compact physical size compared with the conventional horizontally coupled filter made of the single layer. The mixed electric and magnetic coupling can be introduced by two etched circular apertures. And one controllable TZ can be created in the lower stopband for the magnetic-dominant or in the upper stopband for the electric-dominant. To demonstrate the proposed design method, a multilayer SIW BPF for WLAN application has been designed and fabricated, and the measured results show good agreement with the simulated ones.

In this paper, a merged characteristic basis function method (MCBFM) is proposed to analyze the electromagnetic scattering characteristics from conducting targets. A merged characteristic basis function (M-CBF) is newly defined in the MCBFM. Considering the mutual interaction of surrounding blocks, the M-CBF is generated by merging the conventional secondary characteristic basis functions (SCBFs) and the high order characteristic basis functions (HO-CBFs) of each block in the conventional primary characteristic basis function (PCBF). Thus, the true current distribution of the targets is approached by using a single M-CBF reducing the number of CBFs when the incident plane waves (PWs) are certain. The numerical results of a PEC hexahedron demonstrate that the proposed MCBFM improves the accuracy without increasing the number of PWs and the CBFs compared to the improved primary CBFM (IP-CBFM). The results also demonstrate that the MCBFM is capable of effectively reducing the CPU time by 63.38% without losing any accuracy compared to the conventional characteristic basis function method (CBFM). Other results of a PEC cylinder demonstrate that when a considerable computational accuracy is required, the efficiency of the proposed MCBFM is the highest among these three methods.

In this letter, a new coplanar waveguide (CPW)-fed monopole antenna with equilateral-triangular shape is presented and experimentally investigated. The structure under study generates three different center frequencies corresponding to the lower, middle, and upper bands for Wireless Local Area Networks (WLAN) and worldwide interoperability for microwave access (WiMAX) applications. The proposed antenna is analyzed using the Computer Simulation Technology (CST) Software. To validate the simulation results, an experimental prototype of the proposed design is fabricated, tested and measured. The experimental results show a good agreement with the simulated ones.

In a previous work, improved full-wave analytical expressions have been derived for the Sommerfeld Integrals (SIs) describing electromagnetic radiation from a short vertical straight wire located in close proximity to a conductive soil. Such formulas ensure high accuracy of the result of the computation, as well as time savings with respect to conventional techniques used to evaluate the SIs, but unfortunately may be used only when both source and field points are located at the air-medium interface. The scope of this paper is to overcome the limitations implied by the previous approach, and provide series-form expressions for the generated field components that are valid for an arbitrarily stratified medium and for any position of the vertical wire antenna and observation point in the air space above it. The expressions follow from the analytical evaluation of the integral representation for the magnetic vector potential, performed through contour integration after substituting an equivalent pole set for each branch cut of the integrand. Validity, efficiency and accuracy of the developed formulas are illustrated through numerical examples.

In this paper, a technique to identify/synthesize an equivalent circuit of nonreciprocal lossy N-port device is presented. The technique joins the classical procedure discussed in the '60s to the polygon network recently proposed in the literature, which permits to draw an equivalent circuit for reciprocal lossless N-port device in a very simple way. The identication is applied to two microwave devices, a reciprocal lossy iris in WR90 waveguide and a 3-port nonreciprocal lossy circulator. The proposed equivalent circuit could give some information about the agreement of the manufactured device and its design, which usually is developed in the hypothesis of ideal lossless components.

The calculation method for electromagnetic field scattered by antenna placed inside nose dielectric radome is proposed. To obtain the radiation characteristics, we use the calculation method for field generated by radiation aperture given that an arbitrary system of scatterers (particularly, radome) exists in its vicinity. Also, the method for calculating radiation characteristics of antenna system with the same radomes is obtained. Considered numerical results tell us that influence of radome on radiation characteristics can be reduced to minimum for any radome type. Besides, the radome can reduce the radar visibility of antenna system outside of its operating frequency range.

A novel and compact triple-band Y-shaped monopole antenna with dual-polarization characteristics is proposed. The antenna is composed of a partial ground and a microstrip-fed radiating patch that consists of two unequal monopole arms and a circle monopole. The antenna is able to generate three separate impedance bandwidths of 230 MHz (2.30-2.53 GHz), 170 MHz (3.38-3.55 GHz), and 4170 MHz (4.35-8.52 GHz), which can cover both of the WLAN bands (2.4 and 5.8 GHz) and WiMAX band (3.5 GHz). By utilizing different lengths of monopoles, two circularly polarized bands at 2.4 GHz and 5.8 GHz are realized. Moreover, the antenna exhibits monopole-like radiation patterns and stable antenna gains across the operating bands. The effect of the antenna's key structural parameters on its performance was also analyzed.

This paper investigates the phase glint problem involved in interferometric synthetic aperture radar (InSAR) image processing, which refers to the multiple scatterer interference of a single pixel, and studies the distribution of interferometric phase in the case of double scatterer interference. It is found that the value range of the observed interferometric phase is related to several factors including the complex scattering coefficient ratio and interferometric phase difference between the elementary scatterers, and no matter what values of interferometric phases of elementary scatterers are taken, the dynamic range of interferometric phase of phase glintis always. This paper also briefly analyzes the impact of phase glint on classical InSAR image processing and man-made target height retrieval, and it is concluded that the phase glint will induce significant height estimating error. Simulation and real data results verify the conclusion.

Magnetic resonant wireless power transfer (WPT) is an emerging technology that may create new applications for wireless power charging. However, low efficiency resulting from the change of the transfer distance is a main obstructing factor for promoting this technology. In this paper, a method of fast tracking optimum efficiency is proposed. The input impedance value is obtained by measuring the input current. Then the transfer distance is estimated by the input impedance value. The optimum load resistor is obtained under a given transfer distance. In addition, the extended L-matching network is proposed in order to automatically adjust the load resistor. The key parameters of the matching network are also given. The optimum efficiency can be fast tracked by the proposed method as the transfer distance varies. The WPT system and the extended L-matching network are designed. Simulated and experimental results validating the proposed method are given.