Carrier-Auxiliary IF Feedback Crystal-Less LO Generator and Approximate Low-If Receiver Architecture for Energy-Efficient Radio

The battery-free and crystal-less nodes require energy-efficient radio, leading to the design of the ultra-low-power crystal-less receiver. The paper proposes a crystal-less receiver classification method for state-of-the-art works and presents a sub-1mW Class-Ab crystal-less receiver architecture with a carrier-auxiliary intermediate frequency (IF) negative feedback local oscillator (LO) generator and approximate low-IF mode. The proposed LO generator and receiver are implemented using 55nm CMOS technology with a total power of 492.4µW. Without any crystals, the LO frequency based on the bulk acoustic wave (BAW) oscillator maintains a ±6ppm error range from 0°C to 70°C. After locking the LO calibration loop, the phase noise at the 1MHz offset is better than -137dBc/Hz and long-term frequency drift is less than ±0.06ppm in two seconds.