Bias-switched down-conversion mixer for flicker noise reduction in 28-nm CMOS

This paper presents a modified Gilbert-cell mixer employing a novel biasing-scheme used to reduce the high Noise Figure, due to inherently high 1/f noise of MOS transistors. Switching the transistor from strong inversion to accumulation interferes with the self-correlation of the physical noisy process, which leads to a reduction in flicker noise. To illustrate this improvement, a comparison with a conventionally biased mixer is carried. Post-layout simulation results show that this mixer achieves a voltage conversion gain of 2.2 dB, a 1-dB compression point of 3 dBm and a 5 dB reduction in noise figure at 50 kHz, while it draws a current of 13 mA from a single 0.9 V supply. The occupied chip area is 0.5×0.94 mm2. According to author's knowledge this is the first time that bias switching technique is applied to a mixer at mm-wave frequencies.