Design and Analysis of a Wideband K/Ka-Band CMOS LNA Using Coupled-TL Feedback

Abstract

We demonstrate a low power (PD) 22-33 GHz CMOS low-noise amplifier (LNA) with low noise-figure (NF) and small group-delay (GD) variation for 28 GHz 5G system. Body-selfforward-bias (BSFB) technique, i.e., connection of transistor’s body to drain via body resistance, is used for threshold and supply voltage reduction, and substrate leakage suppression. Gain and NF enhancement at the same PD is achieved because lower VDD and higher transconductance (due to larger bias current) are used. Current-reused topology is used for low PD. Coupled transmission -line (TL) feedback neutralization technique is proposed for further gain and NF enhancement. The feedback from output (drain) to input (gate) via gate-drain capacitance (Cgd) can be cancelled by the feedback from drain (through source) to gate via the coupled TL and gate-source capacitance (Cgs). The LNA consumes 12.2 mW and achieves S21 of 16 dB, 3 dB bandwidth (f3dB) of 11 GHz (22-33 GHz), minimum NF (NFmin) of 2.5 dB, average NF (NFavg) of 3.1 dB, and GD variation of ±6 ps for 22-33 GHz, and figure-of-merit (FOM) of 91.7 GHz. Moreover, the LNA achieves input third-order intercept point (IIP3) of -3 dBm. The NF and FOM are one of the best results ever reported for LNAs with f3dB greater than 7 GHz and PD lower than 15 mW.