A feedforward noise and distortion cancellation technique for CMOS broadband LNA-mixer

Abstract

This work presents a circuit technique for broadband LNA-mixer to improve the noise and distortion performance simultaneously. By introducing an auxiliary feedforward path that carries the LNA noise and third-order intermodulation distortion (IM3) with equal magnitude and opposite phase to mixer output, the overall noise and IM3 are reduced while the signal is enhanced. The power overhead is small compared to the conventional tradeoff between the power consumption and linearity performance. The test circuit using a 0.18 process includes a shunt-feedback LNA and two cross-coupled active mixers. All the circuits consume 7.7 mA from a 1.8 V supply. The signal bandwidth is 2 GHz. At 900MHz the voltage gain and noise figure are 19 dB and 6.2 dB respectively. There is 2.7dB NF and 10.1dB IM3 improvements with only 15% power overhead.