Niels Faché

Mixed potential integral equation technique for hybrid microstrip-slotline multilayered circuits using a mixed rectangular-triangular mesh

In this paper, a mixed potential integral equation (MPIE) formulation for hybrid microstrip-slotline multilayered circuits is presented. This integral equation is solved with the method of moments (MoM) in combination with Galerkins method. The vector-valued rooftop functions defined over a mixed rectangular-triangular mesh are used to model the electric and magnetic currents on the microstrip and slotline structures. An efficient calculation technique for the quadruple interaction integrals between two cells in the system matrix equation is presented. Two examples of hybrid microstrip-slotline circuits are discussed. The first example compares the simulation results for a microstrip-slotline transition with measured data. The second example illustrates the use of the simulation technique in the design process of a broadband slot-coupled microstrip line transition. >

Adaptive CAD-model building algorithm for general planar microwave structures

A new adaptive technique is presented for building multidimensional parameterized analytical models for general planar microwave structures with a predefined accuracy and based on full-wave electromagnetic (EM) simulations. The models can be incorporated in a circuit simulator and the time required to calculate the circuit representation of a practical network is reduced by several orders of magnitude compared to full EM simulations. Furthermore, the accuracy of the results is significantly better compared to the circuit models used in state-of-the-art computer-aided design tools.

New fast and accurate line parameter calculation of general multiconductor transmission lines in multilayered media

An enhanced method to calculate the C, L, and R of a multiconductor bus in a multilayered medium is presented. Different board technologies, conductors of complicated shape, and conductors embedded in different layers can be handled without loss of accuracy or substantial increase in CPU time compared with existing simulation techniques. Correct determination of skin effect losses is shown to depend critically on surface charge modeling. Surface charge discontinuities are explicitly taken into account which results in reduced computation time. A further reduction of computation time is obtained by a particular treatment of the calculation of the Greens function. >

Rigorous full-wave space-domain solution for dispersive microstrip lines

The eigenmode problem for the open microstrip line is analyzed in the space domain starting from the calculation of a dyadic Greens function in the spectral domain. The transverse and the longitudinal current are discretized using the method of moments. A point-matching technique is used to impose the boundary condition, i.e., zero tangential electric field, on the strip. The edge conditions at the end points of the strip are explicitly incorporated and special care is taken to accurately retain the static behavior of the field on and near the strip. Special attention is given to the variation of the current distribution as a function of frequency. >

Full-wave space-domain analysis of open microstrip discontinuities including the singular current-edge behavior

A full-wave space-domain analysis is presented for the high-frequency characterization of microstrip discontinuities. This approach solves the electric field integral equation (EFIE) for the surface current density on the microstrip using the method of moments. The current expansion functions incorporate the singular edge behavior of the surface current, yielding a very accurate current modeling. Special attention is devoted to the analytical treatment of the singular terms in the electric field Greens dyadic. The numerical results focus on the S-parameters of some simple microstrip discontinuities and the comparison with results obtained with other techniques and from measurements. >

Generalised Space Domain Green's Dyadic for Multilayered Media with Special Application to Microwave Interconnections

The eigenmode problem for multilayered structures with coplanar or non-coplanar strips is analysed using the space domain Greens dyadic of these structures as the kernel of an integral equation. The integral equation is solved using the method of moments combined with point-matching. The calculation of the Greens dyadic starts in the spectral domain. First, an efficient solution technique is presented to determine the spectral Greens dyadic. Special attention is then devoted to its behaviour for large values of the Fourier variable and to the contribution of this asymptotic part to the space domain Greens dyadic. The behaviour of the fields in the vicinity of the excitation is determined explicitly. The method is illustrated by two typical examples.

New high-frequency circuit model for coupled lossless and lossy waveguide structures

A coupled transmission line model describing the two fundamental modes of any two-conductor (above a ground plane or shielded) dispersive or nondispersive lossless waveguide system is given. The model is based on a power-current formulation of the impedances but does not need an a priori supposition about the power distribution over each transmission line. The analysis is extended to lossy structures and to the multiconductor situation. Impedance calculations for a typical coupled microstrip configuration are used to illustrate the approach. >

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.

Circuit parameters for single and coupled microstrip lines by a rigorous full-wave space-domain analysis

A rigorous full-wave analysis is applied to determine the dispersion characteristics and the impedance matrix of coplanar microstrip lines. It is shown that the impedance definition based on the propagating power and the longitudinal current is the most appropriate one. Examples are given for the single strip, for two coupled strips, either symmetric or asymmetric, and for a three-strip configuration. Some attention is also devoted to the current profiles associated with each eigenmode. >

Adaptive frequency sampling of scattering parameters obtained by electromagnetic simulation

In order to obtain the frequency response, a considerable amount of computation time in electromagnetic simulation is spent on the evaluation of a particular electromagnetic quantity in a user given number of discrete frequencies. The total number of, method of moments, simulations has been limited by using a rational function approximation based on derivative information of that quantity. This technique was used in order to obtain the far-field or induced current of antenna or scattering problems. Little has been done or published on adaptive frequency sampling, i.e. an algorithm for selecting additional frequencies in regions where the approximation exceeds some error measure, and for maximising the information provided by each new sample point. We propose general scheme based on the residual errors of the derivatives. The applicability of this scheme is illustrated with some well chosen examples. In these examples, the S-parameters of microstrip planar structures are calculated by a full-wave electromagnetic simulation.<<ETX>>