Low-power 77-81 GHz CMOS LNA with excellent matching for automotive radars

A low-power and wideband three-stage 77-81 GHz low-noise amplifier (LNA) using standard 90 nm CMOS technology is reported. The T-match technique is utilised to achieve simultaneously wideband input and output impedance matching, wideband power gain (S₂₁) and a wideband noise figure (NF). The LNA consumes 21.1 mW, achieving S₁₁ better than -10 dB for the frequencies 62.3-82.4 GHz, S₂₂ better than -10 dB for the frequencies 62.8-84.6 GHz, S₁₂ better than -29 dB for the frequencies 72-84 GHz and a group delay variation smaller than ±4 ps for the frequencies 77-81 GHz. In addition, high and flat S₂₁ of 13.1 ± 1.5 dB is achieved for the frequencies 72-84 GHz, which means the corresponding 3 dB bandwidth is 12 GHz. Furthermore, the LNA achieves a minimum NF of 6.2 dB at 78 GHz and a NF of 6.8 ± 0.6 dB for the frequencies 75-82 GHz, one of the best NF results ever reported for a CMOS LNA for 77-81 GHz automotive radar applications.