Dual phase shifter

Abstract

A variable dual phase shifter for simultaneously varying the phase shifts in two signal paths by equal and opposite amounts comprises two 90.degree. hybrids in the respective signal paths, and a pair of substantially identical transmission lines connecting output ports of one hybrid to output ports of the other. A number of variable-impedance radio-frequency devices, which are preferably p-i-n diodes, are connected to the transmission lines at positions spaced apart along the length of the lines, the positions on one line corresponding to those on the other line. The impedances of the devices are controlled to create a reflective termination at a selected position on one line and a reflective termination at the corresponding position on the other line, so that the phase shift applied to each signal is determined by the distance of the reflective termination from the respective hybrid. The devices may be arranged in pairs, each device of a pair being coupled to a respective one of the transmission lines. Alternatively, signal devices may be provided, each device being coupled to a respective pair of corresponding positions on the lines via two 1/4-wavelength lines. Two or more of the phase shifters may be connected to cascade to provide progressively finer phase shift steps.