A 30–50 GHz reflection-type phase shifter based on slow-wave coupled lines in BiCMOS 55 nm technology

This paper presents a mm-wave compact, ultra-wideband reflection-type phase shifter (RTPS). This phase shifter is dedicated to phased array transmitter based on LO-path phase shifting for beamforming and beam-steering applications in the sub-mm-wave band. The proposed RTPS is designed using a slow-wave coplanar waveguide coupler and reflective loads. The circuit was fabricated in BiCMOS 55 nm technology. As predicted by simulations, measurement results show a relative phase shift of 61°±1° that is very stable over a wide frequency range from 30 GHz to 50 GHz, with insertion loss of 4 dB ± 1 dB at 50 GHz, leading to a figure-of-merit (FoM) of 12°/dB. The measured return loss is always better than 10 dB across the whole band. The chip area is only 0.18 mm 2 .