Analysis and Design of a 0.6- to 10.5-GHz LNTA for Wideband Receivers

Abstract

A low-noise transconductance amplifier (LNTA) for wideband receivers based on a $g_{m} $ -boosted current mirroring topology that operates over 0.6- to 10.5-GHz is presented. $g_{m}$ boosting relaxes the $G_{m}$ and $S_{11} $ bandwidth (BW) tradeoff and the noise figure (NF) and input matching tradeoff. The active feedback synthesizes a second-order input impedance profile that further extends the $S_{11}$ BW. Despite the high $G_{m} $ obtained over large BW, high linearity is maintained through the predistortion inherent in the current mirroring topology. The LNTA is used in a 65-nm CMOS wideband channelizing iterative downconversion receiver targeting spectrum and signal analysis for cognitive radio and performs active signal splitting across two paths with a total postlayout simulated $G_{m} $ of 242 mS (170 and 72 mS in paths 1 and 2, respectively). $S_{11}$ BW and $G_{m} $ BW both exceed 10.5 GHz. Minimum LNTA NFs simulated in the two paths are 4 and 4.8 dB, respectively. Simulated wideband IIP3 and blocker P1dB are +6 and +1.5 dBm, respectively. Measurements of a direct conversion receiver in path 2 closely match simulations.