Ultra-low power frequency-shift keying demodulator based on injection-locking ring oscillator without using phase locked loop for wireless body area networks

An ultra-low power frequency-shift keying (FSK) demodulator based on injection-locking ring oscillator for wireless body area networks is presented. The proposed system uses the power-efficient injectionlocking ring oscillator (ILRO) to replace the LC oscillator which occupies much more area on chip with higher power consumption. In addition, through the ILRO, the frequency modulated input signal is converted to a full swing rectangular signal, which can be directly demodulated by a chain of down-conversion passive mixers, lowpass filters and a comparator. Power efficiency and simplicity of the proposed structure eliminate conventional FSK demodulator based on power-hungry phase locked loops, which needs to be calibrated by auto-frequency calibrator to periodically compensate the free running frequency deviations due to temperature variations and charge pump leakage current. The proposed FSK demodulator is designed and simulated in 180 nm CMOS technology while consuming only 23.37 mu W from a 0.7 V supply.