Cascading S-Parameters in Plain English: Part 1

Part 1: Introduction

This is part 1 of a 5 part technical series: Cascading S-Parameters in Plain English.

S-parameters describe the frequency domain performance of a device, so engineers can understand and compare devices without needing to be experts about what's 'under the hood'. With a standardized file format called Touchstone (file extension .sNp, where N is the number of ports) S-parameters can easily be shared, plotted, and analyzed.

System architects chain S-parameters from different devices to form a virtual system long before the components are physically built and chained together. Problems are caught very early in the design, saving time and money.

Typically, a signal integrity engineer doesn't have to think about the math of cascading S-parameters because there are so many great software tools which work really well. However, recently I wanted to automate the cascade hundreds or thousands of S-parameters, which required a customized script. Matlab has a library function to cascade S-parameters which I could have used, but I'm a bit thick in the head so I wanted to create an open source cascade function I could use in Octave. I'm glad I took the 'road less traveled', because I learned a lot about the math involved, and hopefully I can now describe what I've learned in a clear, concise way.

The series is broken into 5 parts

Next >> Part 2: S-Parameters in Plain English

By: Matt Wright 7/7/2020

Tags: technical, S-parameters Lead