A 14.5mm2 8nW −59.7dBm-sensitivity ultrasonic wake-up receiver for power-, area-, and interference-constrained applications

The next generation of the Internet of Things is envisioned to include unobtrusive, distributed mm-sized nodes capable of sensing and communicating information about their surroundings. Wake-up receivers (WuRXs) — ultra-low-power receivers that monitor their environment for a wake-up signature — are an important part of this vision, as they can extend the lifetime of a wireless node by keeping it asleep until interrogated. The state of the art in WuRXs, measured in terms of sensitivity and power, has recently been advanced by streamlining the signal path to include fewer power-hungry gain stages and instead obtaining the gain at the chip-antenna interface [1,2]. This has led to excellent power-sensitivity performance, but the accompanying increase in size hampers the applicability of these techniques in size-conscious applications, such as surveillance, asset tracking, and ubiquitous sensing. Moreover, size-reduction methods based on RF antenna miniaturization are fundamentally limited by high antenna Qs at low size-to-wavelength ratios [3]; efficiently matching to these antennas requires, in turn, high-Q passives that are generally unavailable at mm-scale.