A 24 GHz reflective-type phase shifter with constant loss in 0.18 μm CMOS technology

With the aim of achieving constant insertion loss, this paper presents the design of a 24 GHz reflective-type phase shifter (RTPS) integrated with a switched Π-attenuator for phased array transmitters. Three RTPS circuits with hybrid coupler and capacitive-type reflective loads are cascaded to obtain required phase-shift. Accumulation-mode MOS (AMOS) varactors are used as reflective loads for phase control. In order to achieve a compact scheme, the hybrid couplers are designed using lumped elements. A switched Π-attenuator is used in front of the RTPS for gain control. Body switching technique is applied in series switch of the Π-attenuator to improve its switching performance. Consuming zero DC power, the proposed circuit demonstrates a maximal relative phase-shift range of 185°, a constant insertion loss of 10.7 dB, and a worst-case input return loss better than 15 dB at 24 GHz. The circuit is implemented in a standard 0.18 μm CMOS technology and the post-layout simulation results are reported.