Introduction of Frequency Synthesizer

For either implanted or most in vitro medical signal detectors, it is necessary to wirelessly transmit the measured biomedical signal information to the relevant receiving unit. The most crucial component in a wireless transceiver is a frequency synthesizer, which must provide a wide range of bands of frequency and stable oscillation frequency. This chapter first introduces the basic principle of the integer N frequency synthesizer and the stability analysis of its linear model. Then, some key trade-offs when designing an integer-N frequency synthesizer are discussed, including the trade-offs among settling time, phase noise, and reference spurs. Next, each building block in the frequency synthesizer, including phase detector, charge pump, loop filter, oscillator, and frequency divider, are presented. In addition to the integer-N frequency synthesizer, we also briefly introduce the concept of non-integer frequency synthesizer, direct synthesizer, and all-digital phase-locked loop (ADPLL). Finally we discuss in depth the two important units in ADPLL, digital-controlled oscillation (DCO) and time-to-digital conversion (TDC).