James C. Rautio

Microstrip conductor loss models for electromagnetic analysis

This paper describes and rigorously validates single- and multiple-layer models of microstrip conductor loss appropriate for high-accuracy application in electromagnetic analysis software. The models are validated by comparison with measurement and by comparison with converged results. It is shown that in some cases an extremely small cell size is needed in order to achieve convergence. Several effects that make a significant contribution to loss and are not modeled by the classic square root of frequency loss model are investigated including dispersion and current on the side of transmission lines. Finally, the counterintuitive result that there is an optimum metal thickness for minimum planar conductor loss is explored.

Techniques for Correcting Scattering Parameter Data of an Imperfectly Terminated Multiport When Measured with a Two-Port Network Analyzer

Two techniques are described which correct scattering parameter data taken on an N-port device measured with N-2 imperfect terrniuations and a two-port network analyzer. The first technique rises a simple iterative algorithm and may be easily implemented in software. Each iteration reduces the error due to imperfect terminations typically by one decade. The second, more complicated, technique uses a general closed-form solution which requires specially developed Gamma-R parameters of which S-, Y-, and Z-parameters are particular cases. The closed-form solution is completely valid for any termination. The closed-form solution is the limit to which the iterative solution converges. The iterative technique has been implemented in software controlling an HP 8409 automated microwave network analyzer.

EM-Component-Based Design of Planar Circuits

In this article, the author starts with a quick tutorial about the ports used in EM analysis and how they are calibrated. Then, the paper discussed a new development -perfect internal port calibration. Finally, it concludes with a few examples illustrating the impact that perfect internal port calibration will have on microwave design.The author have also introduced a lot of new concepts in this article: perfectly calibrated box wall ports, perfectly calibrated (cocalibrated) internal ports, floating ground references, global ground references, several new component-based design methodologies, and baseline versus test structure validation.

Perfectly calibrated internal ports in EM analysis of planar circuits

Perfectly calibrated internal ports have recently been developed for high frequency electromagnetic analysis of planar circuits. This capability has never before been available. As such, microwave designers are only just now learning the value of such ports. This overview paper describes new and extremely efficient design methodologies that are now practical. For example, if properly prepared, an entire circuit can be EM (electromagnetically) analyzed once and the precise analysis of all subsequent modifications (tuning, tweaking) of the circuit provided essentially instantly. Another capability enabled by perfectly calibrated ports is compact model synthesis. These capabilities are illustrated with examples.

An investigation of microstrip conductor loss

Microstrip conductor loss exhibits complicated behavior that is not generally recognized. Specifically, there are three frequency ranges of interest. At low frequency, current is uniform through the entire cross-section of the line, and the line behaves like a resistor. At medium frequency, the edge singularity forms. In this case, current concentrates on the edge of the line, increasing the resistance. At high frequency, the current splits into two sheets of current, one on top of the line, the other on the bottom of the line. Since microstrip dispersion causes the edge singularity to become larger and current to concentrate on the bottom side as frequency increases, the total resistance increases faster than the normally expected square root of frequency.

Deembedding the effect of a local ground plane in electromagnetic analysis

In electromagnetic analysis of complex planar circuits, it may be necessary to use internal ports, e.g., in locations where surface mount devices might later be attached. These internal ports require a local ground plane for ground reference when access to the global ground reference is unavailable. Even if perfectly conducting, use of such a ground plane still introduces excess phase in the local ground currents. This paper describes how to remove the effect of a lossy or lossless local ground, even including multiple closely spaced ports

An ultra-high precision benchmark for validation of planar electromagnetic analyses

A stripline standard is applied to the validation of planar electromagnetic analysis. Since an exact theoretical expression is available for stripline, a benchmark can be specified to the accuracy to which the expressions can be evaluated. Data for the benchmark accurate to about 10/sup -8/ is provided. A definition for an error metric appropriate for use with the benchmark is illustrated. A means of calculating a precise value of analysis error using the error metric is described. A first order numerical value for the residual analysis error can also be obtained from the calculated S-parameters by inspection. The benchmark can be applied to any planar electromagnetic analysis capable of analyzing stripline. Example results, illustrating absolute convergence of an analysis to 0.05%, are provided. >

Progress in Simulator-Based Tuning—The Art of Tuning Space Mapping [Application Notes]

We discuss tuning space mapping (port-tuning) techniques that can significantly reduce time and effort for design closure. We elaborate on various possible approaches. We distinguish between Type 1 and Type 0 embedding to indicate how tuning elements may be introduced into EM simulations to form suitable tuning models or surrogates. We optimize and update such surrogates iteratively to predict good EM designs. We illustrate the techniques using a simple bandstop filter and demonstrate their power using more complex filter design examples. Finally, we discuss from a physics point of view the possible locations of cuts, the effects of the cutting and reconnection, and we compare models that employ internal cuts with models that consider combinations of submodels.

Synthesis of lumped models from N-port scattering parameter data

A closed form technique is described which allows the synthesis of an N-node lumped network from N-port scattering parameter (S-parameter) data. The synthesis is appropriate for networks where N is very large, for example, high speed digital interconnect networks. The resulting lumped model can be used in SPICE and other simulators. The synthesis is valid for any structure that is small with respect to wavelength. Thus it is also appropriate for synthesizing lumped models of simple discontinuities, such as step junctions and cross junctions. A description of the theory and several examples are provided. >

A new definition of characteristic impedance

It is shown how a novel de-embedding technique, appropriate for electromagnetic analyses, results in a new three-dimensional definition of characteristic impedance, the transverse electromagnetic TEM equivalent characteristic impedance. This new definition is appropriate and unique for all inhomogeneous, as well as homogeneous, media. Further, the resulting characteristic impedance is shown, for a specific microstrip geometry, to have a nonmonotonic dispersion in characteristic impedance. This same dispersion is seen in measurements and is not seen in any of the classical, two-dimensional definitions of impedance.<<ETX>>