A 253-μW 2.4-GHz SAW-Less Mixer-First Uncertain-IF Receiver With Blocker Tolerant for Long-Distance Ultralow-Power IoT

Abstract

This letter presents and designs a 2.4-GHz SAW-less uncertain-intermediate frequency (IF) receiver with blocker tolerant for long-distance ultralow-power (ULP) Internet of Things (IoT). By employing RF downconversion followed by noncoherent digital demodulation, the receiver maintains high sensitivity and low power. A free-running oscillator, without a power-hungry phase-locked loop, is used to generate LO with low power. Instead of a costly and bulky external SAW filter, a two-phase passive mixer combined with a low-power transimpedance amplifier (TIA) is adopted by impedance mapping to solve the low robustness to interferers of the uncertain-IF receiver; as a consequence, an equivalent on-chip RF bandpass high-Q filter is obtained to suppress the interference at the RF input and a good balance is obtained between noise figure, power, and blocker tolerance. Fabricated in a 55-nm CMOS process, at 2.4-GHz LO frequency, the receiver has a 21.4-dB rejection ratio for 10-MHz out-of-band (OB) interference, consuming only $253~\mu $ W under 0.8-V supply with 12.9-dB NF and −6.2-dBm OB-IIP3 at the front end.