A 0.8-V 4.9-mW CMOS Fractional-N Frequency Synthesizer for RFID Application

A 0.8-V fractional-N frequency synthesizer is described, which employs an improved transformer-feedback VCO and a 2-bit third-order SigmaDelta modulator. Implemented in a 0.18-mum CMOS technology, the synthesizer is operated with a 0.8 V supply while consuming 4.92 mW. Phase-noise of -104dBc/Hz at 200-kHz offset and -121dBc/Hz at 1-MHz offset with a reference spur of -84dBc is measured at a center frequency of 1.17 GHz. The synthesizer has a frequency tuning range from 1.06 GHz to 1.4 GHz with a resolution of 25 kHz