Giacomo Bianconi

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.

A Computationally Efficient Technique for Prototyping Planar Antennas and Printed Circuits for Wireless Applications

In this paper, we present a novel procedure for an efficient and accurate electromagnetic simulation of microstrip circuits and printed antennas etched in layered media. The proposed approach, based on a new algorithm referred to herein as the equivalent medium approach (EMA), is applied for a rapid design of the preliminary desired circuit prototype. The illustrated technique yields reliable results and reduces the computational time in comparison with the conventional method of moments (MoM). Some examples that demonstrate the accuracy and the efficiency of the described procedure are included.

An Efficient Technique for the Evaluation of the Reduced Matrix in the Context of the CBFM for Layered Media

In this letter, we present a technique for an efficient evaluation of the reduced matrix in the context of the characteristic basis function method (CBFM) for the simulation of microstrip circuits printed on layered media. The underlying concept is to evaluate the off-diagonal terms of the reduced matrix, which vary much less rapidly then the diagonal ones, in the spectral domain, while the self-interactions are computed in the conventional way. Numerical examples are presented to demonstrate that the fill-time of the reduced matrix is reduced by working in the spectral domain, as compared to the spatial domain evaluation in the conventional CBFM, while maintaining the computational accuracy of the results. Furthermore, the efficiency of the present approach increases rapidly as the number of unknowns in each block is increased .

Volume Integral Equation Analysis of Thin Dielectric Sheet Using Sinusoidal Macro-Basis Functions

In this letter, we present an improvement over the conventional thin dielectric sheet (TDS) formulation for the analysis of thin dielectric sheets. Our focus is to address the problem of scattering from thin penetrable scatterers by developing a volumetric formulation based on the use of macro-basis functions. The electric fields produced by the source basis functions are derived directly, bypassing the summation of scalar and vector potentials. The latter results in a considerable time advantage in comparison to the conventional method of moments (MoM) solution of the volume electric field integral equation (V-EFIE), while the accuracy remains comparable. In contrast to the TDS formulation, both tangential and normal currents are employed so that problems with high and low permittivity, as well as those involving grazing incident angles, can be accurately analyzed. Several examples are reported that show excellent agreement with conventional techniques and demonstrate the effectiveness of the new approach.

Parallelized Multilevel Characteristic Basis function Method (MLCBFM) combined with Adaptive Cross Approximation (ACA) for the analysis of the scattering from electrically large rough surfaces

In this paper, we present a parallel implementation of the Multilevel Characteristic Basis Function Method (MLCBFM) for the analysis of the scattering from electrically large rough surfaces. The Multilevel Characteristic Basis Function method is a natural extension of the conventional mono-level CBFM, which addresses the issues of high computation burden and memory requirement associated with this type of problems. In particular, the MLCBFM is very well suited for parallelization and is characterized by a considerable time-advantage with respect to the conventional CBFM. Furthermore, the Adaptive Cross Approximation (ACA) is incorporated for fast calculation of the interaction sub-matrices.

A High-Order Characteristic Basis Function Algorithm for an Efficient Analysis of Printed Microwave Circuits and Antennas Etched on Layered Media

In this letter, we present a characteristic basis function method (CBFM) algorithm for an efficient “full-wave” analysis of printed microwave circuits and antennas etched on layered media. The main contribution of the proposed approach is a technique for the generation of the primary characteristic basis functions (PCBFs) in conjunction with the employment of high-order characteristic basis functions (CBFs), which enables us to implement a totally general decomposition scheme of the circuit under analysis. Numerical examples are presented to demonstrate the efficiency and the accuracy of the proposed approach.

Characteristic Basis Function Method for efficient modeling of conformal Frequency Selective Surfaces

The paper presents an efficient and accurate technique for the analysis of large, finite and conformal Frequency Selective Surfaces (FSSs) which are not amenable to analysis by using conventional methods. The proposed technique is based on the Characteristic Basis Functions (CBFs) to describe the currents induced on the FSS elements. The reaction integrals needed to derive the reduced matrix elements are either computed in the spatial or spectral domains depending on their separation distance, so as to make the process numerically efficient.

Formulating matrix equations in the context of MoM by using the Dipole Moment (DM) method instead of Green's functions

In this paper we introduce a universal Method of Moment (MoM)-based formulation, which overcomes some of the drawbacks of conventional frequency domain techniques. Formulating the problem in a way that bypasses the evaluation of the electric field as a summation of scalar and vector potential terms enables us to overcome the low-frequency breakdown when applied to the solution of the Surface Electric Field Integral Equation (S-EFIE). The direct evaluation of the electric fields reduces the impedance matrix fill time compared to the conventional MoM. The Equivalent Medium Approach (EMA) can be applied in conjunction with the proposed formulation for the solution of microstrip circuits embedded in stratified environments.

Efficient Numerical Techniques for Analyzing Microstrip Circuits and Antennas Etched on Layered Media via the Characteristic Basis Function Method

The first part of this chapter presents an efficient technique for the electromagnetic analysis of planar microstrip structures, called the Characteristic Basis Function Method (CBFM). In this method, the original problem geometry is segmented into smaller regions called blocks, and high-level basis functions are generated to represent the electromagnetic characteristics of these sections. These basis functions are referred to as the Characteristic Basis Functions (CBFs), and their use leads to a reduced matrix equation system. Since the method only requires the solution a relatively of small-size matrix equations, associated with isolated domains, the computational burden is relieved, and an acceleration of the solve time is achieved. In the second part of the chapter, the Characteristic Basis Function Method is combined with the Equivalent Medium Approach (EMA) for fast and efficient design of microstrip circuits etched on layered media. In particular, the developed EMA method substitutes the stratified environment with an equivalent “homogeneous” medium whose Dyadic Green’s Functions (DGF’s) can be evaluated analytically. The above technique yields reliable results and reduces the computational time in comparison with the conventional Method of Moments (MoM). Some examples that demonstrate the accuracy and the efficiency of the described procedures are included.

A new CBF-generation algorithm for an efficient analysis of microwave circuits and antennas etched on layered media

Summary form only given. Increasing competition in the communication market has fueled the development of increasingly efficient Computer Aided Design (CAD) tools for simulating the performance of microwave circuits. One approach to accelerating the design process is to use a circuit simulator where the microstrip discontinuities are modeled as lumped elements. However, such a network-theory-type of simulator produces accurate results only at low frequencies, and their accuracy degrades rapidly as the operating frequency is increased to the point where the parasitic coupling effects cannot be neglected. One of the most widely employed full-wave algorithms is the Method of Moments (MoM). Though numerically rigorous and accurate, the MoM requires memory and Central Processing Unit (CPU) resources that are orders of magnitude greater than those associated with conventional circuit simulators. Recently, the Characteristic Basis Function Method (CBFM) has been successfully applied for the analysis of Monolithic Microwave Integrate Circuits (MMICs) and antennas etched on layered media. In the original version of this method, the analyzed geometry is decomposed into smaller regions, called blocks, for which high-level basis functions, the Characteristic Basis Functions (CBFs), are generated. Typically, two types of CBFs are calculated, the Primaries (PCBFs) and the Secondaries (SCBFs). The generation of the PCBFs is started by defining appropriate interfaces, i.e., inner ports, between adjacent blocks and considering each section in isolation. To generate accurate results by using the conventional CBFM, it is important to ensure that the inner ports (see Fig. 1) be defined at locations where the effect of the higher-order modes is negligible and the current distribution can be expressed as a linear combination of a forward and a reflected wave. We have developed a new algorithm for an efficient generation of the Primary CBFs which enables us to generalize the decomposition procedure. The partition scheme is user-independent, and allows the interface locations to be arbitrary (see Fig. 1).