26.4 A 2.4GHz 65nm CMOS Mixer-First Receiver Using 4-Stage Cascaded Inverter-Based Envelope-Biased LNAs Achieving 66dB In-Band Interference Tolerance and −83dBm Sensitivity

Abstract

Intensive interest in internet-of-things devices has crowded the ISM bands (e.g., 2.4GHz). A robust receiver for each wireless link in such a coexistence environment is required not only to have high rejection of out-of-band interference but also to tolerate strong in-band interference, which cannot be filtered out by the front-end BAW/SAW devices. Recently, nonlinear suppressors [1, 2] have been demonstrated to amplify a weak desired signal while suppressing strong interferers. In contrast to conventional frequency-dependent techniques, which consume high power to implement high-Q filtering [3–6], the nonlinear suppressor is frequency independent and only needs the envelope information of the interferer to adjust the nonlinear transfer function for interference suppression, reducing power consumption. On the other hand, unlike traditional linear receivers, in particular mixer-first receivers, which require high power to lower LO phase noise to alleviate the impact of reciprocal mixing, nonlinear-suppressor-based receivers can suppress the phase noise inherently and hence have high tolerance to reciprocal mixing. Unfortunately, a major issue for nonlinear suppression is in its severely increased noise figure (NF), which degrades the system sensitivity and limits its potential applications to short ranges.