A comparison of different devices for phase shift measurement at high frequency

Current technologies for measuring phase shifts are reviewed and a new design is reported for phase shift measurements in the 300 MHz region. Attention is given to low and high frequency phasemetry, with a mixing technique for the high frequency end, to vectorial voltmeters with sampling heads, and to synchronous detectors. The phase meters are limited to frequencies up to 10 MHz, while voltmeters can be used up to the UHF range with a precision that is dependent on the relative power level between inputs. Synchronous detectors, though precise, are ineffective at low frequencies. The new phase shift meter employs a heterodyne technique and sinusoidal signals at the input. The signals are mixed and low pass filtered to obtain two voltages, from which the phase shift can be determined even if one of the signals is noisy.