A 1.2 nJ/bit 2.4 GHz receiver with a sliding-IF phase-to-digital converter for wireless personal/body area networks

This paper presents an ultra-low power 2.4 GHz FSK/PSK RX for wireless personal/body area networks. A single-channel phase-tracking RX based on a sliding-IF phase-to-digital conversion (SIF-PDC) loop is proposed to directly demodulate and digitize the frequency/phase-modulated information. The sliding-IF frequency plan reduces the power consumption of the multi-phase LO generation. A phase rotator is adopted in SIF-PDC to guarantee frequency stability, i.e., avoid the frequency pulling by interference or frequency drift. It equivalently transforms the RF signal processing from the I/Q amplitude domain to a digital-phase domain, which saves up to nearly 40% on power consumption and relaxes the digital baseband complexity. A phase-domain linear model of the proposed SIF-PDC is presented to analyze the frequency response. Fabricated in a 90 nm CMOS technology, the presented RX consumes 2.4 mW at 2 Mbps data rate, i.e., 1.2 nJ/b efficiency, and achieves a sensitivity of -92 dBm.