A Low-Power Wide-Band Digital Frequency Synthesizer for Cognitive Radio Sensor Units

This paper presents the design of a wide-band digital frequency synthesizer for cognitive radio sensor units. It is based on an all-digital phase-locked loop, and employs a digitally controlled ring oscillator with an LC tank introduced to extend tuning range and reduce power dissipation. Adaptive frequency calibration based on binary search is used for fast frequency settling. Fabricated in a 65-nm CMOS, the frequency synthesizer has an active area of 0.3 mm(2) and achieves a frequency tuning range of 2.7 to 6.1 GHz, with power consumption less than 22 mW from a 1.2-V supply. Measured phase noise at 6-GHz frequency is 92 dBc/Hz at 1-MHz offset.