A Wide Range Sigma-Delta Fractional-N Frequency Synthesizer With Adaptive Frequency Calibration

A wide range fractional-N frequency synthesizer in 0.18 mu m RF CMOS technology is implemented. A switched-capacitors bank LC-tank VCO and an adaptive frequency calibration technique are used to expand the frequency range. A 16-bit third-order sigma-delta modulator with dither is used to randomize the fractional spur. The active area is 0.6 mm(2). The experimental results show the proposed frequency synthesizer consumes 4.3 mA from a single 1.8 V supply voltage except for buffers. The frequency range is 1.44-2.11 GHz and the frequency resolution is less than 0.4 kHz. The phase noise is -94 dBc/Hz @ 100 kHz and -121 dBc/Hz @ 1 MHz at the output of the prescaler with a loop bandwidth of approximately 120 kHz. The performance meets the requirements for the multi-band and multi-mode transceiver applications.