Using a VNA to find the ‘sweet spot’ when biasing a MMIC — An application

A system to measure the complex S21 at power of a MMIC using a Vector Network Analyzer is described. These measurements have been performed from −50 DBm to +37 DBm with a power span greater than 30 DB in a single sweep. This system can operate over the frequency range of 500 MHz to 50 GHz. This system is used to measure S21 magnitude and phase in addition to bias conditions as a function of input power.