Microstrip

Abstract

Microstrip is probably the most commonly used method of achieving a waveguiding structure [7]. This is due to its simplicity of manufacture (basically PCB technology), light weight (advantages over waveguide), compatibility with integrated circuit processes (both monolithic and hybrid), reasonable range of characteristic impedances, low loss, relatively broad bandwidth, etc. An example of a typical microstrip circuit is illustrated in Figure 6.1. Here a single stage transistor amplifier has been realised. It consists of a field effect transistor with the input line connected to the gate and the output line connected to the drain. The source is connected through the substrate to the ground metallisation. The circuit also has stub matches on the input and output, bias lines for the d.c. supply to the transistor and d.c. blocking capacitors at the input and output to decouple the circuit. The capacitors are discrete components mounted between gaps in the microstrip lines.