Conventional Spectral Domain Approach Research Articles

Neurospectral modeling of rectangular patch with rectangular aperture in the ground plane

In this study, we propose an artificial neural network in conjunction with spectral domain approach (SDA), for fast and accurate determination of the resonant frequency and half-power bandwidth of rectangular patch over the ground plane with rectangular aperture. The performances evaluation of the neurospectral method reveals superiority over the conventional SDA model in terms of errors and time. The results obtained from the neurospectral method are in very good agreement with the experimental and theoretical results available in the literature. Finally, numerical results for the effect of rectangular aperture dimensions on the resonant characteristics of the rectangular patch are also investigated.

Analysis of Finite Conformal Frequency Selective Surfaces via the Characteristic Basis Function Method and Spectral Rotation Approaches

An efficient characteristic basis function (CBF)-based method is proposed to analyze conformal frequency selective surfaces (FSS) that are not amenable to analysis by using conventional numerical methods typically used to model infinite, planar, and doubly periodic FSSs. The technique begins by employing the CBFs to describe the currents induced on the elements. The reaction integrals needed to derive the reduced matrix elements are computed either in the spatial domain, or spectral domain, depending on the separation distance between the blocks, so as to make the process numerically efficient. The spectral domain integrals are evaluated by making use of the spectral rotation (SR) on the spectra of the CBFs to alleviate the computational burden to be associated with full three-dimensional (3-D) Fourier transform, which is required in the conventional spectral domain approach applied to nonplanar geometries. Numerical results from the new method have good agreement with the fully spatial characteristic basis function method (CBFM) and the conventional method of moments (MoM). However, the required central processing unit (CPU) time is greatly reduced.

Air Gap Tuning Effect on the Resonant Frequency and Half-power Bandwidth of Superconducting Microstrip Patch

An accurate analysis of an air gap tuned high Tc superconducting microstrip an- tenna is presented. To include the efiect of the superconductivity of the microstrip patch in the Full wave analysis of the tunable rectangular microstrip patch, a surface complex impedance is considered. This impedance is determined by using London's equation and the model of Gorter and Casimir. Numerical results obtained are found to be in excellent agreement with the the- oretical and experimental data available in the literature. Finally, numerical results for the air gap tuning efiect on the operating frequency and bandwidth of the high Tc superconducting microstrip antenna are also presented. Rectangular microstrip patches can flnd an application in microwave integrated circuits as planar resonators for oscillators and fllters. Also, rectangular microstrip patches can be used as resonant antennas fed by means of either coaxial probes, or microstrip lines. Since the bandwidth of mi- crostrip patch resonators and antennas around their operating resonant frequencies is known to be very narrow, it is important to develop accurate algorithms for the computation of those res- onant frequencies. The resonant frequency value of the rectangular microstrip patch depends on the structural parameters, and it is evident that if the resonant frequency is to be changed, a new microstrip antenna is needed. In order to achieve tunable resonant frequency characteristics, an adjustable air gap layer can be inserted between the ground plane and the substrate, resulting in a two-layer structure (1,2). Apart from tunable microstrip patches, in the last few years, there has been a growing interest in the use of superconducting materials in microwave integrated circuits, which is due to their main characteristics, such as: very small losses, which means low-attenuation and low-noise, very small dispersion up to frequencies of several tens of GHz, smaller devices due to the lower losses, which leads to larger integration density and reduction in the time of propagation of the signals in the circuits (3). In this paper, a rigorous Full-wave analysis of an air gap tuned high Tc superconducting mi- crostrip antenna is presented. To the best of our knowledge, this structure has not been analyzed previously. Only results for the case of perfectly conducting patch have been reported in the open literature (1,2). In Section 2, the authors provide details of the application of the Galerkin's method in the Fourier transform domain to the analysis of high Tc superconducting microstrip antennas with air gaps. In Section 3, the validity of the solution is tested by comparing the computed results with theoretical and experimental data available in the literature. Numerical results for the air gap tuning efiect on the operating frequency and half power bandwidth of the high Tc superconduct- ing microstrip patch antenna are also presented. Finally, concluding remarks are summarized in Section 4. 2. OUTLINE OF THE NUMERICAL PROCEDURE The high Tc superconducting microstrip patch antenna considered in this work is shown in Figure 1. It was obtained by depositing a superconducting patch of thickness e on a dielectric layer. The dielectric layer of thickness d2 is characterized by the free-space permeability 0 and the permittivity 0, r (0 is the free-space permittivity and the relative permittivity r can be complex to account for dielectric loss). An adjustable air gap layer of thickness d1 is inserted between the substrate and the perfectly conducting ground plane. Following the conventional spectral domain approach, the Fourier transform domain relationship between the surface electric fleld at z = d1 +d2 and surface

Using selective asymptotics to accelerate dispersion analysis of microstrip lines

A selective asymptotic technique (SAT) to accelerate the elements of the impedance matrix in the conventional spectral-domain approach (SDA) is presented. Instead of using the full asymptotic expression of the Green's functions, only those parts which cannot be evaluated in closed form are approximated by their asymptotic expressions. The resulting expressions are more accurate and systematic, as no additional parameter is introduced. The technique is applied to determine the effective dielectric constant of an open microstrip line to demonstrate its efficiency.

Dispersion characteristics of open microstrip lines using closed-form asymptotic extraction

A full-wave spectral-domain method with an asymptotic extraction technique is formulated for multilayer microstrip lines. This formulation provides a simple closed-form representation of the asymptotic part of the impedance matrix by using Chebyshev polynomial basis functions with the square-root edge condition and the asymptotic behaviour of the Green's function. The formulation is applied to open microstrip lines. Numerical results, in the form of the effective dielectric constants, are presented for the dominant mode. It is shown that the proposed method significantly reduces the computational time and improves the accuracy over the conventional spectral-domain approach (SDA).

Closed-form asymptotic extraction method for coupled microstrip lines

The effective dielectric constants of a symmetric coupled microstrip line operating in the dominant mode are solved by using a closed-form formula of the asymptotic part of the impedance matrix elements. Using this asymptotic closed-form solution, the finite upper limit for numerical integration in the evaluation of the impedance matrix elements is significantly reduced. This results in improved computational efficiency for determining the /spl epsiv//sub reff/ of a coupled microstrip line while retaining a good accuracy compared to the conventional spectral domain approach (SDA).

An efficient approach to modeling of quasiplanar structures using the formulation of power conservation in spectral domain

An enhanced spectral domain approach (SDA) is developed for analysis of complex quasi-planar transmission lines. The method is based on a combination of the spectral domain formulation and power conservation theorem. The relationship between electric and magnetic fields is established inside dielectric layers by using the conventional SDA while the characteristic equation related to interface conditions is derived through the power conservation theorem. Maintaining the inherent advantages of the SDA, this technique is able to easily handle more complex quasi-planar structures. Generalized power formulation is also presented to calculate characteristic impedance. Convergence behavior is discussed considering the nature of power conservation. Various finlines with finite thickness of conductors are analyzed to demonstrate its applications.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Dispersion and attenuation characteristics of coplanar waveguides with finite metallization thickness and conductivity

A new approach of modifying the conventional spectral-domain approach is proposed for an analysis of the coplanar waveguide whose signal strip and ground planes have finite thickness and conductivity. By introducing suitable equivalent sources in the slot and signal strip regions, the problem can be significantly simplified by reducing the two-dimensional numerical integration into the one-dimensional one, thus it can be treated as easily as the conventional spectral-domain approach. By this modified approach, both the phase constant and attenuation constant can be determined simultaneously without using the assumption that the metallization thickness is much larger or smaller than the skin depth. In this work, comparison with published theoretical and experimental results is presented to check the accuracy of the new approach's results. In particular, the effective dielectric constant /spl epsiv//sub eff/ and attenuation constant a of a coplanar waveguide with finite metallization thickness and finite conductivity are discussed in detail, together with the current distributions along the signal strip and ground planes.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Modified spectral-domain approach for microstrip lines with finite metallisation thickness and conductivity

A modified spectral-domain approach is proposed for an analysis of the microstrip line whose signal strip and ground plane have finite thickness and conductivity. To improve the accuracy of the results, all three components of the strip current which have three-dimensional dependence are included in the analysis. With the basis functions properly chosen, this new approach can be treated as easily as the conventional spectral-domain approach. By this modified approach, both the phase constant and attenuation constant can be determined simultaneously without using the assumption that the skin depth is much larger or smaller than the signal strip thickness. In this work, comparison with published theoretical and experimental results is presented to check the accuracy of the new approach. In particular, the effective dielectric constant and attenuation constant of a microstrip line with finite metallisation thickness and finite conductivity are discussed in detail, together with the longitudinal current distributions along the signal strip.

Numerically efficient analysis of planar microstrip configurations using closed-form Green's functions

An efficient technique for the analysis of a general class of microstrip structures with a substrate and a superstrate is investigated in this paper using newly-derived closed-form spatial domain Green's functions employed in conjunction with the Method of Moments (MoM). The computed current distributions on the microstrip structure are used to determine the scattering parameters of microstrip discontinuities and the input impedances of microstrip patch antennas. It is shown that the use of the closed-form Green's functions in the context of the MoM provides a computational advantage in terms of the CPU time by almost two orders of magnitude over the conventional spectral domain approach employing the transformed version of the Green's functions. >

Frequency-dependent solution of suspended microstrip line with tuning septums

The frequency-dependent effective dielectric permittivity and equivalent characteristic impedances of the technically most relevant modes of the suspended microstrip line with tuning septums are derived using the conventional spectral domain approach. Normalised numerical results are presented in a very large frequency band.