An automated matching network incorporating a six-port reflectometer

Abstract

In this thesis an automated matching network is investigated as a means to reduce mismatch loss in circuits whose impedance characteristics vary during operation. The automated matching network incorporates a six-port network to measure impedance and a tunable circuit is implemented using varactor diodes to provide continuously variable impedances. A novel implementation for two-port measurements using a single reflectometer is presented. The thesis concentrates on variable gain amplifier applications as these are common in wireless applications and matching is rarely maintained over the operating range of the device. A six-port reflectometer is implemented using off-the-shelf components. The tunable network is implemented using a miniature hybrid microwave integrated circuit (MHMIC) process with varactor diodes used as variable capacitances. Gain matching of a transistor amplifier is tested under various device biases. The project establishes design guidelines for a tunable matching network using continuously variable impedances. The feasibility of the automated matching network concept is also proven. Based on the results, several proposals are made for future work using automated matching networks.