A millimeter-wave fully differential transformer-based passive reflective-type phase shifter

This paper presents a millimeter-wave fully differential compact transformer-based passive reflective-type phase shifter (RTPS). The proposed RTPS design employs two transformer-based 90° couplers and two transformer-based multi-resonance reflective loads, offering low-loss and an ultra-compact chip size. A proof-of-concept design at 62GHz is implemented in a standard 130nm BiCMOS process with a core area of 480μm-by-340μm. It achieves a wide phase shifting range (up to 367°) and a low insertion loss (IL) (3.7dB<|IL|<10.2dB) at 62GHz. It also performs phase shifting with a constant insertion loss at a loss variation of less than 0.7dB. Full-span 360° phase interpolation is achieved from 58GHz to 64GHz with a worst-case minimum IL of 10.72dB. Compared with the reported 60GHz RTPS integrated in silicon, our design is the first to achieve a full-span 360° phase shift, has the lowest IL and the smallest IL variation, and presents the best figure-of-merit (FoM) of 36.26°/dB.