A 2.4GHz 830pJ/bit duty-cycled wake-up receiver with −82dBm sensitivity for crystal-less wireless sensor nodes

This paper describes a 2.4GHz Wake-up Receiver (WuRx) designed to operate with low-accuracy (≪0.5%) frequency references [1], enabling crystal-less and thus low-cost wireless sensor nodes (WSNs). Robustness to frequency error is achieved by combining non-coherent energy detection with a broadband-IF superheterodyne architecture, and by using a pulse-position-modulated (PPM) impulse radio (IR) modulation scheme [2]. The Rx front-end and the LO generator are duty-cycled at pulse level, thereby reducing the power consumption to less than 420µW, which is more than adequate for use in WSNs [2]. PPM-IR also enables the realization of an interferer-robust receiver without the use of bulky off-chip RF filters [3,4]. This 65nm CMOS fully integrated WuRx employs a duty-cycled LO generator and achieves a sensitivity of −82dBm at a data rate of 500kb/s with an energy efficiency of 830pJ/bit.