The use of an ultra-low-power wake-up receiver (WuRx) can dramatically reduce the overall power consumption of a wireless link and is especially attractive for the increase of the battery lifetime of a wireless sensor node (WSN). Several recent works [1–3] demonstrated the feasibility of achieving sub-100nW WuRxs. The key is to remove the power-hungry RF LNA by utilizing the high passive gain from the external matching network (MN). Unfortunately, the resulting envelope-detector-first (ED-first) architecture suffers two problems and limits practical applications. First, their moderate sensitivity with sub-100nW power is only achieved at a very low data rate bps) with high latency mS). Second, the ED-first architecture is vulnerable to in-band interference and thus limits their use in the crowded ISM band. To cope with the in-band jammers, techniques such as the time-domain integrator [1], PID controller [2], and auto-offset-control-loop [3] are used to adapt the comparator threshold to suppress the DC offsets caused by the CW interferers. Yet, these loops are too slow such that AM interferers can deteriorate the carrier-to-interference-ratio (CIR). On the other hand, frequency-translation WuRx [4] or envelope-detector (ED) based WuRx with two-tone modulation (TTM) [5–7] can improve interference resilience. However, they either consume too much power (e.g., [4–5, 7] or require an off-chip MEMS filter [6].