Microwave and Radar Engineering

7

Scattering Matrix for Waveguide Components

7.1 INTRODUCTION

The analysis of networks or devices at low frequencies commonly uses circuit parameters such as Z parameters, Y parameters, and ABCD parameters. These parameters are derived based on terminal voltage and current measurements. They require the application of short- and open-circuit terminations for evaluation. A brief description of these parameters is given in Section 7.8.

However, it is very difficult to measure voltages and currents at microwave frequencies because of the following reasons:

• They are distributed values and vary with their position in microwave structures.
• Active devices become unstable when they are terminated with open or short circuits at high frequencies.