24.3 A high-linearity CMOS receiver achieving +44dBm IIP3 and +13dBm B1dB for SAW-less LTE radio

Abstract

LTE-advanced wireless receivers require high-linearity up-front filtering to prevent corruption of the in-band signals by strong out-of-band (OOB) signals and self-interference from the transmitter. SAW duplexer filters are generally used for this purpose, but supporting the plethora of existing and new bands becomes troublesome with separate filters for each band. In this paper we explore the possibility of combining an isolator with on-chip filtering. However, even with 15dB isolation, the on-chip filter needs to deal with up to +10dBm TX leakage and −15dBm OOB blocking, which requires an extremely high IIP3 around +50dBm and IIP2 around +90dBm. Recently inductorless tunable N-path-filter-based receivers achieved >10dBm compression point and good IIP3 of 20 to 30dBm. In order to further improve the receiver linearity to approach the extremely high IIP3 requirement for a SAW-less receiver, a high-linearity N-path bandpass/notch filter topology and receiver architecture are proposed in this paper.