A 5 GHz CMOS frequency synthesizer with novel phase-switching prescaler and high-Q LC-VCO

A phase-locked loop (PLL) frequency synthesizer with a novel phase-switching prescaler and a high-Q LC voltage controlled oscillator (VCO) is presented. The phase-switching prescaler with a novel modulus control mechanism is much more robust on process variations. The Q factor of the inductor, I-MOS capacitors and varactors in the VCO are optimized. The proposed frequency synthesizer was fabricated by SMIC 0.13 μm 1P8M MMRF CMOS technology with a chip area of 1150 × 2500 μm². When locking at 5 GHz, the current consumption is 15 mA from a supply voltage of 1.2 V and the measured phase noise at a 1 MHz offset is −122.45 dBc/Hz.