A 225-μW Interference-Tolerant Receiver With Shared Wireless LO and Envelope-Tracking Mixer Achieving -104-dBm Sensitivity

Abstract

This article presents a 915-MHz interference-tolerant receiver (RX) with a shared wireless local oscillator (LO) and an envelope-tracking (ET) mixer for low-power Internet-of-Things (IoT) networks. For applications featuring a large number of RXs, the deployment of a shared wireless LO can enhance the energy efficiency of the system. The proposed ET mixer retrieves phase-following (PF) LO pulses from the wireless LO, aligning them, respectively, with the peak and valley of the radio frequency (RF) input signal. This allows the RX to track the target peak and valley envelopes of the RF input signal, improving mixer gain and conversion quality (Q). Moreover, eliminating the integrated LO conserves system power and reduces area. The RX also employs intermediate-frequency (IF) calibration to derive an adaptive IF1 LO based on the uncertain frequency of the wireless LO, thus creating a known IF2 with a narrow bandwidth to enhance sensitivity, interference tolerance, and channel selectivity. Fabricated in a 65-nm CMOS process, the RX achieves a sensitivity of -104 dBm with a -50-dBm wireless LO, while occupying 0.2-mm2 active area and consuming $225~{\mu }$ W at a 10-kb/s data rate. The achieved RX figure-of-merit (FOM) is 180 dB. The sensitivity loss is within 10 dB with the wireless LO power ranging from -69 to -30 dBm. With the -50-dBm wireless LO, the RX exhibits 44- and 32-dB tolerances to 100-kb/s and 5-Mb/s on-off-keying (OOK) interference with 5-MHz offset.