Frequency Synthesizer With Dual Loop Frequency and Gain Calibration

A 3600-MHz phase-locked loop based frequency synthesizer for UMTS applications has been developed in 0.18 μm CMOS. It incorporates a VCO frequency and loop-gain calibration technique that allows an integrated VCO frequency tuning range of 28% and a low VCO gain ( KVCO of 30 MHz/V. The loop-gain calibration can compensate for not only variations in VCO gain and divider modulus, but also charge-pump current and loop filter capacitance to an accuracy of 5%. The PLL settles in 150 μs including frequency and gain calibrations. No switches are used in the loop filter. The output phase noise at 1-MHz offset is -123 dBc/Hz and the integrated phase error (1 kHz-2 MHz) is 1.26 °.