Optimisation of signal phase split in vector modulator phase shifters

Abstract

Choosing a phase split larger than 90 degrees influences the output characteristics of a vector modulator operated as a continuous phase shifter. It is shown that for a vector modulator with a phase split larger than 90 degrees , less amplitude variation is required to achieve a specified phase range as compared to a conventional design with a split of 90 degrees . Analytical expressions are given for phase and amplitude errors in the output signal resulting from errors in the phase split and amplitude of the signal vector components. By assuming simple models for errors in the signal components, the authors have performed calculations showing that a larger phase split reduces phase errors, although amplitude errors might be larger. In addition, the overall maximum power gain is reduced as the square sine of the phase split, leaving a trade-off.