A Ku-Band Vector Modulated Active Phase Shifter by Using Phase Compensated Auxiliary Transistors

This paper presents a 12.5-19 GHz 5-bit vector modulated active phase shifter. The phase shifter is comprised of an input matching network, a resistor-capacitor (RC)-resistor-inductor (RL) polyphase filter (PPF), a vector modulator and an output matching network. To improve phase shifting accuracy, a vector modulator with a cascode structure and phase compensated auxiliary transistors is proposed. These auxiliary transistors are integrated into the vector modulator to adjust the current ratios of the I/Q paths. Additionally, coupled inductors are introduced between the CS and CG stages to neutralize parasitic capacitance of the transistors and enhance the gain. In the layout, an optimized double butterfly RC-RL PPF layout is proposed, minimizing orthogonal signal distortion caused by layout asymmetries. The phase shifter is fabricated in 110-nm CMOS technology. Measurement results show that the phase shifter achieves a 3-dB bandwidth of 12.5-19 GHz. The measured root-mean-square (RMS) phase and gain errors are less than 4° and 0.55 dB, respectively. The chip area is 0.6 mm².