Over the last few decades, as fast development in electronic and communicational science and technology, the practical use in this field has been promoted faster and faster. Signal generator, which can be called the heart of electronic system, has powerful effect on the whole electronic system .It has been a hot question on how to produce a signal generator of low cost, high performance and high stability. That is the technology of frequency synthesize. The performance and cost of the signal generator are directly influenced by the design method of the frequency synthesizer. So it is still a big challenge for the designer to accomplish it in a proper way. Recent years, the fast developing technology of the phase-locked frequency synthesizer has been being one of the main design methods of the signal generator by its superiority.Phase-locked loop (PLL) is negative feedback self-driven circuit. The application of the PLL is not just the frequency synthesizer. Why we choose PLL as a proper method is because of its high performance. First, the PLL frequency synthesizer has a very broad frequency range. Second, in so broad a frequency range, it can produce a series of frequency points with the same high precision and stabilization as reference frequency. Third, recently, a lot of ways to resolve the disadvantages of the PLL frequency synthesizer appear, such as, the appearance of fractional N divider solves the problem of frequency resolution, and the delta-sigma processing method reduces the level of phase noise.