Direct modulation 4 phase PSK modulator

摘要

A 4 phase PSK modulator is implemented using micro-strip printed circuit technology and produces a 4 phase PSK modulated carrier by direct modulation of an RF carrier. Implementation is by means of three strip-line hybrids and two semiconductor diode phase shifters. The RF carrier is applied to one input of the first hybrid, and the other input is terminated in its characteristic impedance. The outputs of the first hybrid are connected through the semiconductor diode phase shifters to the inputs of the second hybrid. The outputs of the second hybrid are directly coupled to the inputs of the third hybrid, and the 4 phase PSK output is available from each output of the third hybrid. The semiconductor diode phase shifters are controlled to produce either 0 DEG or 180 DEG phase shifts, and by changing the state of the diode phase shifters, a separate output phase is generated for each of the four possible diode states.