Design of a 9.75-10.25 GHz Phase Shifter in 180 nm CMOS Process with 360° Phase Tunability for Phased Array System

To direct the far field radiation beam, phased array antenna systems require electronic phase shifters to supply various input signal phases in the individual elements. In this paper, a three-stage differential phase shifter that is compatible with phased array antenna systems operating at 9.75-10.25 (X band) GHz is proposed. The proposed phase shifter is designed in 180 nm CMOS process and consists of three identical varactor loaded LC stages. A Pi-network topology is used for the single stage phase shifter which consists of a fixed inductor and four varactors. Based on post layout simulation, the inductor value is optimized to include the inductance due to the metal signal lines. The stages are connected via 2-bit PMOS switches which controls the signal flow routes between the stages. The layout of the proposed phase shifter is completed and the signal line length and width connecting the phase-shifted signal to the output are kept the same to assure phase shift accuracy. In order to improve the return loss, input and output matching networks are also designed based on the impedance value from the post layout simulation. The phase response of the phase shifter is controlled using the 6-bit switching of the three stages and fine tuned by controlling the varactor control voltages. The proposed phase shifter achieves 0 degrees - 360 degrees phase shift with almost flat phase response over the 500 MHz bandwidth.