G. Conciauro

Dispersion characteristics of substrate integrated rectangular waveguide

Dispersion properties of the substrate integrated rectangular waveguide (SIRW) are rigorously obtained using the BI-RME method combined with the Floquets theorem. Our analysis shows that the SIRW basically has the same guided-wave characteristics as the conventional rectangular waveguide. Empirical equations are derived from the calculated dispersion curves in order to estimate the cutoff frequency of the first two dominant modes of the SIRW To validate the analysis results, an SIRW guide was designed and measured. Very good agreements between the experimental and theoretical results were obtained.

Fast S-domain modeling of rectangular waveguides with radially symmetric metal insets

This paper describes the application of the boundary integral-resonant-mode expansion (BI-RME) method to the modeling of rectangular waveguides with metal insets. It extends to more complicated radially symmetric insets, a method recently introduced by the authors, for the simple case of a cylindric post. In this extension, a self-consistent new theory is presented, which fully exploits the peculiarities of the considered class of structures, thus straightforwardly leading to the system equations. The efficiency of the BI-RME method, already demonstrated in the wide-band modeling of arbitrarily shaped waveguide components, is further enhanced in the particular application considered in this paper because the currents on the waveguide walls are not involved in the calculation. For this reason, the method-of-moments discretization of the field equations leads to a mathematical model of order much smaller than in the general BI-RME approach and in other boundary integral methods. Due to the state-space formulation of this model, a wide-band representation of the generalized admittance matrix of the structure is easily found in the form of a pole expansion in the S-domain by the calculation of a reasonably small number of eigensolutions of a matrix eigenvalue problem. The method is very fast and reliable, and permits the realization of a very efficient software, well suited for inclusion in computer-aided design tools for microwave circuit design. Some examples show the efficiency of the method, including the application to multiple and slanting insets and to the modeling of an evanescent-mode filter.

Combination of generalized admittance matrices in the form of pole expansions

This paper describes a novel algorithm for the determination of the wide-band mathematical model of a waveguide component, segmented into elementary blocks of known characteristics. Starting from the Y-matrices of the blocks, given in the form of pole expansions in the frequency domain, the algorithm yields the overall Y-matrix in the same form. Therefore, it can be applied iteratively to find the pole expansion of the Y-matrix of larger and larger waveguide structures. The algorithm is particularly useful if the Y-matrix of the blocks are obtained by the boundary-integral-resonant-mode-expansion (BI-RME) method, which yields the Y-parameters just in the desired form. Two examples show that the joint use of the BI-RME method and of the algorithm described in this paper results in a very accurate and fast numerical code, well-suited for the wide-band modeling of complex waveguide structures.

Generalized Y-matrix of arbitrary H-plane waveguide junctions by the BI-RME method

This paper describes the extension of the BI-RME method to the determination of the generalized Y-matrix of arbitrary H-plane waveguide junctions. The method yields this matrix in the form of a pole expansion in the frequency domain. The generalized matrix is very useful in the wideband analysis of complex structures that include the junction as a building block. An example demonstrates the advantages of this extension of the BI-RME method.

On the evaluation of modal coupling coefficients by contour integrals

The coupling coefficients between two waveguide modes or between a waveguide and a Floquet mode can be written in terms of line integrals on the boundary of the smaller waveguide. However, some of these integrals give rise to indeterminate forms when the cutoff frequencies of the two modes coincide, thus making these expressions useless from a numerical point of view. In this paper, alternative line-integral expressions are derived, which remove the indeterminacy and are applicable also when the cutoff frequencies are very close or even coincident.

MoM/BI-RME analysis of boxed MMICs with arbitrarily shaped metallizations

In this paper, we propose a novel approach for the analysis of shielded microstrip circuits, composed of a number of thin metallic areas with arbitrary shapes and finite conductivity, embedded in a multilayered lossy medium. The analysis is based on the solution of an integral equation (IE) obtained by enforcing the proper boundary condition to the electric field on the metallic areas. The IE is solved by using the method of moments with entire domain basis functions, which are numerically determined by the boundary integral-resonant-mode expansion (BI-RME) method. The use of the BI-RME method allows for the efficient calculation of the basis functions independently on the shape of the domain, thus permitting the analysis of a wide class of circuits. Two examples demonstrate the accuracy, rapidity, and flexibility of the proposed method.

Generalized admittance matrix of arbitrary E-plane waveguide junctions by the BI-RME method

This paper describes an efficient boundary integral technique for the determination of the quasi-static generalized Y-matrix of building blocks of E-plane waveguide components. This matrix is a part of the pole expansion of the Y-matrix in the frequency domain. Calculating the remaining part by the BI-RME method, and using the technique described in this paper, we obtain a very efficient algorithm for the wideband modeling of E-plane building blocks. Some examples demonstrate the efficiency of the algorithm.

A new algorithm for the wide-band analysis of arbitrarily shaped planar circuits

An algorithm for the wideband analysis of the two-dimensional model of a planar circuit is described. The planar circuit is considered to be enclosed in a regularly shaped (rectangular or circular) resonator, and the electric and magnetic fields are derived from the Greens functions of this resonator by integrating over the periphery of the circuit not coinciding with the regular shape. The special form used for the Greens functions makes it possible to derive the Z-parameters in a special form, similar to Fosters series, but converging much more rapidly. The calculation requires the determination of a reduced number of resonances of the planar circuit, which are obtained by an integral equation approach leading to a linear eigenvalue problem. The algorithm was implemented in an efficient computer-aided design (CAD) routine, named ANAPLAN, which is briefly described. >

Fast optimization, tolerance analysis, and yield estimation of H-/E-plane waveguide components with irregular shapes

This paper presents an algorithm for the wide-band optimization of H- and E-plane waveguide components with irregular shapes. The algorithm is based on the boundary-integral-resonant-mode expansion method, used in conjunction with a variational technique, which permits the determination of the objective function and of its gradient by solving a single electromagnetic problem. The same technique allows for performing a sensitivity analysis to check the effect of the mechanical tolerances on the performance of the component and to estimate the yield for a given manufacturing technology on a large-scale production. Many examples demonstrate the effectiveness of the proposed algorithm.

Full-Wave Analysis and Design of Dielectric-Loaded Waveguide Filters Using a State-Space Integral-Equation Method

A full-wave analysis method for waveguide filters based on dielectric loaded resonators is proposed in this work. For such purpose, a state-space integral-equation formulation has been developed, and the efficient numerical evaluation of all matrices and singular integrals related to the method has been detailed. The novel technique has been first validated through the accurate analysis of a dielectric loaded rectangular cavity, and a simple stopband structure based on such basic building block. Then, making use of a computer-aided design tool, a four-pole bandpass filter based on dielectric loaded resonators has been efficiently designed. The accuracy of the proposed method has been validated through successful comparisons with data from technical literature and available commercial software.