A low-power 5-75-GHz common-gate subharmonic mixer in 65-nm CMOS

Direct conversion architectures have the advantage of no image frequencies, fewer components and lower cost. However local oscillator (LO) leakage reduces receive sensitivity, causes LO pulling, and is a challenging problem for direct conversion transceiver design. A mixer using the 2nd-order harmonic of LO is thus desired to address this issue. The sub-harmonic mixer, proposed in this paper, is based on switching common-gate structure using 65-nm CMOS technology. With a current consumption of 2 mA at 1.5 V supply, the mixer achieves measured voltage conversion gain better than 3 dB for frequencies between 5 to 75 GHz. In the 57 to 66-GHz frequency band, the LO to RF port isolation is better than 38 dB and the noise figure is 14.8 dB when driven with a 30-GHz quadrature LO input.