A $-$ 79 dBm 7.56 nW 433 MHz Wake-Up Receiver With Interference Suppression for IoT Application

In this paper, we present an ultra-low power wake-up receiver (WuRX) with effective interference suppression capability. A specific robust design has been implemented to address the common interference issues in the industrial, scientific, and medical (ISM) frequency band. A mathematical expression is derived in this paper for the minimum signal-to-noise ratio (SNR) required by the comparator at which a envelope detector first (ED-first) WuRX can detect the wake-up message in the presence of interference. Aiming to meet the minimum SNR requirements, a quasi-direct coupling (QDC) baseband buffer scheme is proposed. Compared to the output SNR of traditional AC schemes, the QDC baseband buffer scheme achieves a 4.16 dB increase in output SNR under optimal conditions. To solve the problem where traditional comparator calibration schemes require recovery time after sudden disappearance of interference, the multipath signal detection (MPSD) scheme proposed in this paper can immediately detect information following the disappearance of interference, which improves detection efficiency. The WuRX is manufactured in 65nm LP process, consuming 7.56nW at a 0.4V power supply, with a sensitivity of
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79dBm in the 433MHz ISM band. Under continuous wave (CW) interference, the receiver achieves a signal-to-interference ratio (SIR) of
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31dB at a frequency offset of 1MHz.