A 25–55 GHz CMOS sub-harmonic direct-conversion mixer for BPSK demodulator

In this paper, a sub-harmonic direct-conversion Gilbert-cell mixer using 0.13-frac14m CMOS technology for BPSK demodulator is presented. For sub-harmonically pumping, a four-way quadrature divider using 90deg coupler and 180deg balun is implemented in the CMOS process [6]. For wide bandwidth, distributed transconductance stage design and high impedance compensation line are incorporated into the sub-harmonic Gilbert-cell design. The presented sub-harmonic Gilbert-cell mixer achieves an excellent conversion gain flatness of-5.5 plusmn1.5 dB from 25 to 55 GHz. Finally, the direct-conversion sub-harmonic Gilbert-cell mixer is used as a BPSK demodulator and features good demodulation quality.