A −124-dBm Sensitivity Interference-Resilient Direct-Conversion Duty-Cycled Wake-Up Receiver Achieving 0.114 mW at 1.966-s Wake-Up Latency

Abstract

This article presents an interference-resilient high-sensitivity binary frequency-shift keying (BFSK) multi-channel wake-up receiver (WuRX) supporting 900-MHz bands for low-power wide-area network (LPWAN) applications. The proposed WuRX uses a direct-conversion architecture, a frequency-to-energy demodulator, and a 4096-bit correlator. Direct conversion using a 50%-to-25% duty-cycle conversion mixer and two-stage ring voltage-controlled oscillator (VCO) minimizes the power consumption. The frequency-to-energy demodulator offers a process-voltage-temperature (PVT) variation-tolerant symbol recovery based on an image rejection <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$n$ </tex-math></inline-formula> -path filter (IRNF), a poly-phase filter (PPF), and a quadrature envelope detector (ED). The 4096-bit correlator provides a digital processing gain of about 17 dB, improving both the sensitivity and the selectivity. To reduce the power consumption further, the proposed WuRX supports an asynchronous duty-cycling operation based on repetition of the wake-up code. Implemented in the 55-nm complementary metal–oxide–semiconductor (CMOS), the proposed WuRX achieves sensitivity of −124 dBm in the always-on mode while dissipating 781 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{W}$ </tex-math></inline-formula> . For the duty-cycling mode with wake-up codes repeated 15 times, the proposed WuRX exhibits the same sensitivity of −124 dBm with reduced power consumption of 114 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{W}$ </tex-math></inline-formula> and extended wake-up latency of 1.966 s. The proposed WuRX shows robust interference resilience with a signal-to-interference ratio (SIR) of −76 dB at a 20-MHz offset against a continuous wave (CW). The CMOS radio module, including the proposed WuRX, showed packet-error rates (PERs) of 0% and 5.7% in the 4.8- and 9.8-km ground-to-ground wireless communication tests, respectively.