W-band low-noise amplifier using λ/2-spiral-inductor-based positive feedback technique in 90 nm CMOS

A low-power and wideband low-noise amplifier (LNA) for 77 GHz automobile radar and 94 GHz image radar systems using 90 nm CMOS technology is reported. Half-wavelength (λ/2)-spiral-inductor-based positive feedback technique is used at the common-source input stage for gain (S 21 ) enhancement. Moreover, T-match technique is utilized to achieve simultaneously wideband input and output impedance matching, and wideband S 21 and noise figure (NF). The LNA consumes 6.3 mW and achieves S 11 and S 22 better than − 10 dB for frequencies of 76.9–94.1 GHz and 77.2–96.7 GHz, respectively. That is, the corresponding input and output matching bandwidth are 17.2 GHz and 19.5 GHz, respectively. Additionally, high and flat S 21 of 13.5 ± 1.5 dB is achieved for frequencies of 77–99.5 GHz, which means the corresponding 3-dB bandwidth is 22.5 GHz. Furthermore, the LNA achieves NF of 6.3–8.1 dB for frequencies of 75–100 GHz and excellent FOM (figure-of-merit) of 5.97 GHz/mW, one of the best results ever reported for a CMOS LNA with similar operation frequency.