A 2.4-GHz Crystal-Less GFSK Receiver Using an Auxiliary Multiphase BBPLL for Digital Output Demodulation With Enhanced Frequency Scaling

This brief presents a 2.4-GHz crystal-less GMSK/GFSK phase-tracking receiver (PTRX) that employs a multiphase bang-bang PLL (BBPLL) as an auxiliary loop to perform multibit oversampled demodulation. A divider-less 30-MHz BBPLL with a 16-stage ring voltage-controlled oscillator (VCO) and 15 bang-bang phase detectors (BBPDs) works as a clock-less phase-to-digital converter (PDC) and improves demodulation SNR with control polarity reversal and frequency scaling. A prototype 2.4-GHz PTRX with the reference-less BBPLL is implemented in 65 nm and performs 1-Mb/s GMSK demodulation with -84-dBm sensitivity. Experimental results show that the proposed receiver can achieve high slew-rate transient performance for increased frequency deviation with the multiphase BBPLL-based demodulation.