90‐degree differential phase shifters using meander‐line networks

A differential phase shifter uses two all-pass networks with different electrical lengths and obtains a constant differential phase output from the difference in phase characteristics of the two networks. Since conventional phase shifters basically consist of two-wire coupling lines and uniform lines, they are relatively large. In this paper, two types of differential phase shifters are proposed to obtain compact circuit geometry by using meander-line networks. First, meander-line all-pass networks are used to construct the phase shifter. Although the differential phase output bandwidth becomes small compared with that of conventional phase shifters, the circuit geometry can be made compact. Next it is shown that the phase shifter consisting of transformers with transformation ratio 2:1 can match the input port and that it can be miniaturized while yielding a similar differential phase output. Within the design band the output ratio of the two networks becomes close to unity and hence the phase shifter can be used as a branching circuit with constant phase difference.