Thanks to the advance of semiconductor and communication technology, the wireless communication market has been booming in the last two decades. It evolved from simple pagers to emerging third-generation (3G) cellular phones. In the meanwhile, broadband communication market has also gained a rapid growth. As the market always demands hi- performance and low-cost products, circuit designers are seeking hi- integration communication devices in cheap CMOS technology. The phase-locked loop frequency synthesizer is a critical component in communication devices. It works as a local oscillator for...