A 60-GHz Low-Power Active Phase Shifter With Impedance-Invariant Vector Modulation in 65-nm CMOS

This study presents the design and analysis of a 60-GHz low-power active vector-sum phase shifter with 5-bit phase resolution. An impedance-invariant variable gain amplifier (VGA) is proposed and applied to the vector modulator. The proposed VGA not only demonstrates low phase and impedance variations during gain control but also high linearity under low supply voltage. Moreover, it reduces the gain/phase error in vector modulation. In addition, the transformer-based current-reuse technique is adopted to enhance the gain of the phased array channel while consuming low dc power. The prototype circuit implemented in 65-nm CMOS technology consumes only 5 mW of dc power and occupies an area of 0.3 mm(2) (excluding pads). The measurement results of the prototype circuit reveal that the proposed phase shifter achieves an average gain of -3.8 dB (including a 2-dB loss of the measurement balun), an rms gain error of 0.25-0.72 dB, and an rms phase error of 3 degrees-7 degrees in the 3-dB bandwidth from 51 to 66.3 GHz. The measured input 1-dB compression point is observed to be higher than -1.1 dBm at 60 GHz.