A millimeter-wave 4-bit digital phase shifter

A technique for designing millimeter-wave 4-bit digital phase shifter circuit is presented. The proposed phase shifter were fabricated using a reflection-type circuit for 180° and 90° and a loaded-line-type circuit for 45° and 22.5° which is operated at center frequencies from 33.9GHz to 34.5GHz. Especially, the circuit is made in 7111 main microstrip and each cell of 180° and 90° consist of a 3dB coupler loaded by four PIN diodes. Compared with the traditional circuits, they can reduce insertion loss and return loss while reduced maximum phase error. The simulation result shows that the insertion loss and return loss of the phase shifter is very low over the whole band of 33.9GHz-34.5GHz, and the phase shifter accuracy is ±1° while the VSWR is less than 1.2. It is shown that the reflection-type is more efficient for the phase control method.