A 24GHz reflective-type phase shifter with constant loss in 0.18?m CMOS technology
With the aim of achieving constant insertion loss, this paper presents the design of a 24GHz reflective-type phase shifter (RTPS) integrated with a switched ?-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 ?-attenuator is used in front of the RTPS for gain control. Body switching technique is applied in series switch of the ?-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 10.7dB, and a worst-case input return loss better than 15dB at 24GHz. The circuit is implemented in a standard 0.18?m CMOS technology and the post-layout simulation results are reported.
phase shifter cmos hybrid coupler varactor switched attenuator