A Phase Measuring System for Short RF Pulses

The phase measuring system described in this paper was developed primarily for the purpose of determining the phase variation along a narrow RF pulse generated by a high-power traveling-wave tube. This techniques is also suitable for the precision measurement of relative phase shifts that arise when the tube parameters are varied over their operating range. It is a two-channel system that employs a balanced modulator to derive an offset signal and utilizes a homodyne detector to translate the phase information to a high intermediate frequency. This particular null technique ensures high accuracy even when a comparison is to be made over a wide range of signal amplitudes.