A Clockless Wake-Up Receiver and Crystal-Less Clock Recovery Architecture for ULP EQS-HBC Nodes

Wake-up receivers (WuRXs) in energy-constrained wireless transceivers typically rely on always-on clocks and crystal oscillators for sampling, correlation, and carrier synchronization, increasing standby power, area, and system cost. Eliminating these timing references enables leakage-level idle operation but introduces challenges in achieving low-latency asynchronous wake-up and crystal-less carrier synchronization. This work presents a 65-nm CMOS first-silicon architectural proof-of-concept featuring a clockless WuRX and a crystal-less clock recovery unit (CRU) for electro-quasistatic (EQS) human-body communication (HBC) systems. The proposed WuRX adapts directly to incoming on-off keying (OOK) data without a local sampling clock, enabling leakage-level idle listening. A successful first-silicon wake-up event is demonstrated 80~μ s after the start of the applied wake-up packet. Following wake-up, the proposed CRU dynamically extracts the carrier clock from the incoming data using a hybrid open- and closed-loop timing-recovery scheme, achieving measured frequency acquisition within 80~μ s from CRU enable under the reported nominal measurement condition, without an external crystal reference. Measured through-body experiments demonstrate successful asynchronous wake-up and on-the-fly clock extraction using fully integrated silicon, validating the first-silicon feasibility of eliminating both always-on clocks and external frequency references in ultralow-power (ULP) HBC nodes.