G. Coen

Automatic derivation of equivalent circuits for general microstrip interconnection discontinuities

The techniques presented in this paper allow one to automatically derive equivalent LC-networks for general lossless microstrip interconnection discontinuities. The method is completely based on physical considerations and does not involve any fitting procedure. The technique is quite fast, and the resulting networks are closely related to the physical structure. Due to the fact that we only use lumped passive circuit elements, the structures under consideration are assumed to be small as compared to the electrical wavelength. The extension of our technique to multilayered planar structures with vias is possible. It is also possible to deal with lossy dielectrics, finite conductivity metallizations, and radiation. The main application area of our technique is the modeling of interconnection discontinuities in high speed digital circuits.

Comparison between two sets of basis functions for the current modeling in the Galerkin spectral domain solution for microstrips

A frequently used technique for the numerical full wave analysis of planar microwave passive structures is the method of moments (MoM). A very important determinant for the accuracy and efficiency of this technique is the choice of the basis functions used in the approximation of the unknown current components. The application of several types of entire and subsectional domain basis functions has been proposed in the literature. However, little comparison has been made between different types of basis functions. In this paper, a comparison is presented between two sets of frequently used subsectional domain basis functions for the canonical case of the microstrip transmission line. The emphasis in this paper is on the relative accuracy, the convergence and the computational efficiency of both sets of basis functions. The intent of the paper is primarily to be an eye opener for the implications of the choice of the basis functions. >

Automatic equivalent discrete distributed circuit generation for microstrip interconnection discontinuities

This paper presents a novel technique that allows one to derive so called discrete distributed networks for general microstrip interconnection discontinuities that are small compared to the wavelength. Our interest is in high speed digital circuits so the requested bandwidth is about 5 GHz. The basis of our technique is the classical MoM solution of an appropriate mixed potential integral equation, using a mesh of rectangles and triangles. However, instead of combining the current and charge couplings to a system impedance matrix, they are interpreted as an equivalent circuit, as in the PEEC-method, developed by Ruehli (1974). Then, energy principles are used to reduce this network. In this circuit reduction, no fitting procedure is needed, which has a serious impact on calculation time. Also, for design purposes, we have made our technique such that there exists a one to one correspondence between an element in the equivalent circuit, and some part of the physical structure. The paper is restricted to two-ports on pure microstrip substrates.

Elimination of mutual couplings in discrete element networks arising from the modeling of high speed digital interconnections

Ruehli et al. (1992) have presented a technique that allows an automatic derivation of equivalent discrete element networks for general interconnection structures that are valid up to very high frequencies. When we restrict ourselves to the lower frequencies that are typical for high speed digital circuits, then several approximations are possible. For the case of microstrip interconnection discontinuities, the authors have presented a possible reduction approach (1994). One of the consequences of the fact that we restrict ourselves to the low frequency range, is that a number of mutual couplings become redundant. This aspect has not been investigated. In this paper, we shall first explain where this redundancy comes from. Then, we shall present both a formal mathematical and a more practical approach for the elimination of mutual couplings in practical networks. We conclude this paper with an illustrative example.

An automatic mesh complexity reduction scheme for the derivation of equivalent circuits of microstrip interconnection discontinuities

This paper describes an extension of the techniques presented previously (see IEEE APS-S Intl. Symp. Proc., 1994). The purpose of the main technique that is presented here is to reduce the mesh complexity in the MoM analysis of a general planar structure. The technique is such that the information from the original dense mesh is not neglected, but rather taken into account in a different way. Using the techniques presented in this paper, we can now derive equivalent RLC-networks for general multiport microstrip interconnection discontinuities, in a fully automated way. The method is completely based on physical considerations, and does not involve any fitting procedure. Due to this, the technique is quite fast, and the resulting networks are closely related to the physical structure. We shall present an example of this network derivation procedure at the end of this paper.

Reduction of circuit complexity by elimination of internal nodes in the circuit modeling of planar interconnection structures

The authors have developed a novel technique for the automatic derivation of equivalent RLC-networks for general microstrip interconnection discontinuities. An essential step in the technique is the reduction of the complexity of the complex lumped circuit model obtained by applying the method of moments to the considered microstrip discontinuity. In this paper, we present the concepts, algorithms and mathematical manipulations of this reduction scheme. The mathematics are based on the tensor analysis of networks and on network diakoptics, both developed by Kron.

Partial element description (PED) for planar interconnection structures

The authors have developed a technique that allows one to automatically derive simple full wave equivalent lumped networks for general planar interconnection discontinuities. In this technique, we start from a so called partial element description (PED) of the given structure. This is a network interpretation of the numerical analysis of the given structure, analogous to Ruehlis PEEC method (Ruehli et al. [1-3]). The circuit elements in this network are complex and frequency dependent. Then, this PED is reduced using a very general network reduction technilque, which was also developed by the same authors. The last step is the extraction from this PED of a network that has only real and frequency independent circuit elements. In this paper, we will discuss the derivation of the PED for microstrip structures.