A 5.6 dB NF Two-Stage 110 - 125 GHz LNA Gain-Boosted by RC-over-Neutralization for Radar Applications in 28 nm CMOS

This paper presents a two-stage differential LNA operating at around 120 GHz achieving a measured noise figure of 5.6 dB. We obtain a gain of 6.65 dB per stage by means of the RC-over-neutralization technique. Hence, the LNA exhibits an overall measured gain of 13.3 dB using only two stages and therefore occupies a minimal core area of only $0.03 \mathrm{~mm}^{2}$. Lossy over-neutralization technique has been used so far mainly for power amplifiers, while in this work we apply it for an LNA. Furthermore, we extend this approach by adding an explicit neutralization resistance, which provides another design degree of freedom, enabling independent choice of $R_{\mathrm{n}}$ and $C_{\mathrm{n}}$ during the physical circuit implementation. We analyze systematically the $R_{\mathrm{n}}$ and $C_{\mathrm{n}}$ values to achieve simultaneously optimal NF and gain. We show that $R_{\mathrm{n}}$ causes only a minimal NF degradation, yet it enables boosting gain per stage. The circuit is realized in 28 nm bulk CMOS process and dissipates only 25.2 mW from a single 0.9 V supply. It achieves in measurement an RF-bandwidth of 15 GHz and $\mathrm{IP}_{1 \mathrm{~dB}}$ linearity of -17.3 dBm. The presented two-stage LNA can be useful for area saving in D-band receivers.