A method to increase the bandwidth of a series-fed dipole pair (SDP) antenna by using a parasitic strip pair director is presented. A conventional SDP antenna consists of two dipole elements having different lengths and a ground reflector, which are serially connected with a transmission line. In the proposed antenna, a parasitic strip pair director is appended to the conventional SDP antenna. Initially, a conventional SDP antenna that operates in a frequency range of 1.7-2.7 GHz is designed by optimizing the lengths of the elements (two dipoles and ground reflector) and the distances between these elements. Subsequently, a parasitic director containing a pair of strips is placed near the top dipole element to improve the bandwidth and gain of the conventional SDP antenna. Then, the effects of the location and size of the director on the impedance bandwidth and realized gain are investigated. A prototype of the proposed antenna is fabricated on an FR4 substrate, and its performance is compared with that of the conventional SDP antenna. The experimental results show that the proposed antenna has an enhanced bandwidth of 1.63-2.97 GHz (58.26%) and an increased gain of 5.6-6.8 dBi.

A scalable and highly accurate RF symmetrical inductor model (with model error of less than 5%) has been developed from more than 100 test structures, enabling device performance versus layout size trade-offs and optimization up to 10 GHz. Large conductor width designs are found to yield good performance for inductors with small inductance values. However, as inductance or frequency increases, interactions between metallization resistive and substrate losses render the use of large widths unfavorable as they consume silicon area and degrade device performance. These findings are particularly important when exploiting the cost-effective silicon-based RF technologies for applications with operating frequencies greater than 2.5 GHz.

Circuit and multipolar approaches are presented to investigate the correlation between absorption and scattering processes in 2D problems. This investigation was inspired by earlier works of Prof.R.E. Collin, which pointed out deficiencies of the Th'evenin/Norton circuit models to evaluate the scattered and absorbed powers associated with receiving antennas and, thus, encouraged research on new analytical tools to address these problems. Power balance results are obtained with both circuit and multipolar approaches that are fully consistent. This analysis serves to illustrate how the correlation between absorption and scattering processes results in upper bounds for their power magnitudes, as well as stringent design trade-offs in both far-field and near-field source and scattering technologies.

This paper presents a class of polarization-agile arrays with controlled sidelobes. The architecture is based on the interleaving of two independently polarized sub-arrays through a deterministic strategy derived from Almost Difference Sets (ADSs). The efficiency, flexibility and reliability of the proposed design technique is assessed by means of a set of numerical simulations. Moreover, selected experiments aimed at comparing the performances of the presented approach with state-of-the-art design are provided. Finally, mutual coupling effects are numerically analyzed and discussed.

In this paper, two kinds of dual-band bandpass filter (BPF) based on a single square ring resonator are presented, which are realized by loading capacitance or inductive stubs, respectively. Even-odd-mode analysis is applied to explain their model characteristics. One filter is implemented by loading a pair of capacitance stubs, and both in-band couplings can be tuned in a reasonable range. Another filter is completed by loading a pair of inductive stubs, and the first and second passband center frequencies can be controlled independently. For demonstration, two filters operating at 2.45/5.25 GHz and 2.4/5.25 GHz are designed and fabricated. The simulated and measured results show good agreements.

This paper presents method of moments based analysis of high-gain broad-band waveguide broad-wall longitudinal slot array antenna. Initially a basic two-element slot array antenna has been analyzed, and corresponding scattering parameter data have been obtained. The theoretical data have been compared with experimental data and Ansoft HFSS's simulated data to validate the proposed method. The excellent agreement obtained between the results validates the analysis. After validating the methodology attempts have been made to design a broad-band high-gain slot array antenna. An 18-element slot array antenna has been designed, fabricated and tested. The fabricated antenna provides a high gain over large band width.

Complementary split ring resonators (CSRRs) are applied on a UWB Vivaldi antenna to eliminate some unwanted narrow band services. Based on the sensitivity of band rejection, we successfully separate the whole radiating patch of a Vivaldi antenna into three subareas: The feeding area, where the Vivaldi antenna demonstrates a highly sensitive response to CSRRs with a narrow notching band; The transition-area, where CSRRs transfer a ultra wideband (UWB) Vivaldi into a narrow band antenna; and the rest area, where CSRRs are proved to have little effects on the antenna bandwidth property. A band notch Vivaldi antenna with 4.8 GHz to 5.4 GHz rejection band is demonstrated to verify our study from both simulated and measured results.

In a time domain Marching-on-in-degree (MOD) solver based on a Galerkin implementation of the Method of Moments (MoM), it is observed that the matrix elements for the matrix to be inverted contain integrals that are similar to the ones encountered in a frequency domain MoM solver using the piecewise triangular patch basis functions. It is also observed that the error in the evaluation of the matrix elements involving these integrals are larger in the time domain than those involved in the frequency domain MoM solvers. The objective of this paper is to explain this dichotomy and how to improve upon them when using the triangular patch basis functions for both the time and the frequency domain techniques. When the distance between the two triangular patches involved in the evaluation of the matrix elements, are close to each other or when the degree of the Laguerre polynomial in a MOD method is high, the integral accuracy will be compromised and the number of sampling points to evaluate the integrals need to be increased. Numerical results are presented to illustrate this point.

The frequency dependent characteristics of grounding system buried in half homogenous earth model have been discussed before; however, the importance of mutual inductive and capacitive effects on the grounding problems in both frequency and time domains is unclear. In order to study the importance of the mutual inductive, capacitative and conductive effects on the grounding problem in both frequency and time domains, hybrid method, which is a hybrid of Galerkin's method of moment and conventional nodal analysis method, has been used to study the dominant factor among the mutual inductive, capacitive and conductive effects in the paper.

In through-the-wall radar imaging (TWRI), wall returns are often stronger than target returns, which make the targets behind walls invisible in the radar image. Spatial filtering that relies on the removal of the spatial zero-frequency components is a useful way for wall-clutter mitigation. Unfortunately, it applies to through-the-wall radar (TWR) with synthetic aperture array only. In this paper, a method based on spatial signature is proposed to suppress the wall-clutter in multi-input and multi-output (MIMO) TWRI. Firstly, the traditional spatial filtering method is discussed, as well as the reasons for the inapplicability for MIMO TWR. Secondly, the wall and target spatial signatures based on MIMO array are analyzed, respectively. The results indicate that the former has stability and symmetry, whereas the latter not. Thirdly, according to the above differences, a new method, symmetry subtraction, is applied to describe the wall-clutter suppression procedure. Finally, simulation results demonstrate that the proposed method is efficient in mitigating the wall returns and highlighting the targets.

In this article, a novel coplanar waveguide (CPW)-fed miniaturization folded slot antenna for wireless local area network (WLAN) application is proposed and investigated. The multi-operating bands are achieved by folded slot antenna with slot loading. The parametric analysis of the antenna is done by the available electromagnetic solver HFSS11. The designed antenna has a small overall size of 28 mm×30 mm, and operates over the frequency ranges, 90 MHz (2.40 GHz-2.49 GHz), 400 MHz (3.4 GHz-3.8 GHz) and 870 MHz(5.17-6.04 GHz) suitable for WLAN 2.4/5.2/5.8 GHz and WiMAX 3.5/5.5 GHz applications. The proposed antenna is developed, and its measured characteristics are in good agreement with the simulated results. The experimental results show that the antenna gives dipole-like radiation patterns and good antenna gains over the operating bands. In addition, effects of main parameters of the triple-frequency for the design on the electromagnetic performance are examined and discussed in detail.

In this paper the derivation of a rigorous expression of the input admittance of a coaxially fed, infinite, lossy parallel plate waveguide (PPWG) is presented. The derivation makes use of the dyadic Green's function of the PPWG expressed as series a cylindrical wave-functions. Losses into the dielectric plates and on the conductors are considered rigorously. The approximation used in results presented in the past literature are critically discussed. Numerical experiments are performed to show the effects of the finite conductivity on the input impedance of the PPWG.

A finite element method based on the first order system LL* (FOSLL*) approach is derived for time harmonic Maxwell's equations in three dimensional domains. The finite element solution is a potential for the original field in a sense that the original field U is given by U = L*u. The Maxwellian boundary data appears as natural boundary condition. Homogeneous Dirichlet boundary conditions for the potential must be imposed, and they are circumvented with weak enforcement of boundary conditions and it is proved that the sesquilinear form of the finite element system is elliptic in the space where the Dirichlet boundary conditions are satisfied weakly.

We provide a sucient condition to select the parameters of Type 3 Non-Uniform Fast Fourier Transform (NUFFT) algorithms based on the Gaussian gridding to fulll a prescribed accuracy. This is a problem of signicant interest in many areas of applied electromagnetics, as for example fast antenna analysis and synthesis and fast calculation of the scattered elds, as well as in medical imaging comprising ultrasound tomography, computed axial tomography, positron emission tomogr aphy and magnetic resonance imaging. The approach is related to the one dimensional case and follows the work in A. Dutt and V. Rokhlin, SIAM J. Sci. Comp. 14 (1993). The accuracy of the proposed choice is rst numerically assessed and then compared to that achieved by the approach in J.-Y. Lee and L. Greengard, J. Comp. Phys. 206 (2005). The convenience of the strategy devised in this paper is shown. Finally, the use of the Type 3 NUFFT is highlighted for an electromagnetic application consisting of the implementation of the aggregation and disaggregation steps in the fast calculation of the scattered eld by the Fast Multipole Method.

This paper presents the technique to solve inhomogeneous profiles in the cross section of the helical rectangular waveguide. We present the technique to solve inhomogeneous dielectric profiles and the relation to the method of the propagation of electromagnetic fields along a helical waveguide with a rectangular cross section. The inhomogeneous examples will introduce for a dielectric slab, for a rectangular dielectric profile, and for a circular dielectric profile, in a rectangular metallic waveguide, in the cross section of the helical waveguide. This model is useful to improve the output results of the output power transmission in the cases of space helical waveguides, by increasing the step's angle or the radius of the cylinder. The application is useful for space helical waveguides in the microwave and the millimeter-wave regimes.

We study the electrodynamic characteristics of a strip loop antenna located on the surface of a circular column filled with a resonant magnetoplasma and surrounded by a homogeneous isotropic background medium. The antenna current is excited by a time-harmonic voltage creating an electric field with the azimuthal component in a narrow gap on the strip surface. It is shown that the current distribution and input impedance of such an antenna are strongly influenced by the presence of an infinite number of propagating quasielectrostatic modes that are guided by a column containing a resonant magnetoplasma.

A new method for the theoretical analysis of the third-order intermodulation distortion (IM3) in barium strontium titanate (BST) thin film interdigital capacitors (IDCs) on r-plane sapphire substrates is presented. Two circuit topologies-the dual and series dual BST varactor circuit-are proposed and their theoretical models along with simulated and measured results are presented. Low IM₃ is demonstrated and experimentally verified. By proper selective biasing, very low nulls are observed in both dual and series dual BST varactor circuit topologies which indicate minimum distortion. The measured first nulls are achieved at ±13 V and ± 20 V for the dual and series dual topologies respectively. These results demonstrate the potential of incorporating these highly linear BST varactors in silicon on sapphire (SoS) applications.

A high-gain and low-cost circularly polarized antenna array is proposed, which consists of four sequentially rotated circularly polarized square slot antennas (CPSSA). A novel feeding network is applied to the four-element array antenna, which results in increasing the axial ratio (AR) bandwidth. The measured impedance bandwidth for VSWR<2 is around 3.48 GHz (3.75 GHz~7.23 GHz) exhibiting a 2.8 GHz (3.8 GHz~6.6 GHz) 3 dB axial-ratio bandwidth (ARBW) and 9.05 dBic peak gain. The simulated and measured results are in good agreement with each other to verify the design.

A hybrid approach to find the optical response of periodic photonic structures to incident light is presented. The approach is based on a scattering matrix combination of the Finite Element Method (FEM) and the Fourier Modal Method (FMM). Optical response calculations include: scattering in both reflection and transmission directions, absorption and electric and magnetic field distributions inside the structure. The approach is tested on a structure --- composed of dielectric and metallic materials --- that is periodic in one direction. An analysis of the calculation accuracy shows that the approach depends on the subdivision into FEM and FMM domains and that the optimal subdivision depends on the calculations frequency range as well as on the structure geometry. For testing, we use the commercial FEM solver contained in CST Microwave Studio and a based on C/C++ Fourier Modal Method implementation.

This paper presents the performance analysis of Bistatic Interferometer BAsed on Spaceborne SAR (BIBASS). As a bistatic system with general configuration, the system response of BIBASS is azimuth/range dependent. Taking into account this peculiarity, the appropriate theoretical framework is developed to make a more accurate evaluation of the performance of BIBASS. Firstly, the interferometric features are studied. Then, considering all kinds of de-correlation factors, a comprehensive investigation of coherence of such a system is conducted, followed by the relative height accuracy analysis. The theoretical analysis and simulation show that BIBASS, with the ability of high-precision height measurement, can be widely applied as a novel remote sensing measurement system.