An Improved Highly-Linear Low-Power Down-Conversion Micromixer for 77 GHz Automotive Radar in SiGe Technology

This paper proposes a method to improve the non-linearity of the differential RF signals, the noise figure and conversion gain in the existing micromixer through inserting a transistor that is connected in diode form in the mirrored RF branch. These improvements are demonstrated by three micromixers designed at different frequency bands. A 77 GHz micromixer in 0.25 mum SiGe:C BiCMOS technology using the proposed method is fabricated and measured. Additionally, current injection technique is applied in the circuit to increase gain and reduce power consumption. 13.4 dB gain, 18.4 dB NF and 1.4 dBm OP_1dB are achieved with 176 mW power consumption at 4.5 V. To the authors´ knowledge, this is the first reported 77 GHz micromixer