Reference phase-shifter for measuring high power microwave impedance by using a phase modulation method

A basic mechanical phase-shifter is described and proposed for use as a reference circuit for impedance measurements with a phase modulation method. It consists of a section of a curved rectangular waveguide, the length of which is mechanically varied with a stepper motor. The phase-shifter functions without gears. It can be used successfully in industrial set-ups with a pulsed or CW generator which are of low stability in frequency and in amplitude.