A Ka-band Vector-Sum Phase Shifter in 65nm CMOS for Phased Array Receivers

Abstract

In this paper, a Ka-band vector-sum phase shifter with high quadrature precision I/Q signal generator and a new type of digitally controlled variable gain amplifier is presented. Specifically, the parasitic capacitance of the input common source stage of the I/Q signal generator is absorbed by an additional inductor in parallel resonance. In effect, the quadrature precision between the I/Q branch has been improved across the entire Ka-band. A variable gain amplifier based on digital control of transconductance was also proposed, which is equivalent to a cascode structure. The equivalent cascode transistor is composed of a 3x4 transistor array, and the transconductance of the overall circuit is adjustable by turning some of them on or off through programmable digital control signals. The proposed Ka-band vector-sum phase shifter is simulated with the TSMC 65nm CMOS process. It achieves an RMS phase error of 1.7°-2.2° and an RMS magnitude error of 0.9-2.1dB over 27-40GHz while covering a 360° phase range in steps less than 5.625°. The maximum DC power consumption is 8.9mW under 1.2V supply voltage, and the chip area is 0.399mm2.