100MHz Low Phase Noise Crystal Oscillator PLL Frequency Multiplier

As the technology of communication and radar develops rapidly, the system’s requirements of signal quality have become increasingly higher. For instance, the indexes like phase noise and stability degree of frequency largely imply the quality of one system. As the reference signal of frequency synthesizer, crystal oscillator has long been known as the "heart" of electronic products, thus a nickname demonstrates its significance. However, in some sorts of systems, system reference signal is the only signal, but it can not be used as reference signal of frequency synthesizer. Therefore, it is necessary to unify system reference signal and frequency synthesizer reference signal, and we find that phase locked crystal oscillator can resolve this problem properly. On the condition of guaranteeing the quality of phase noise, phase locked crystal oscillator is able to unify references signals of system and frequency synthesizer, and the oscillator is widely applied.This thesis introduces basic theories of phase-locked loop firstly, then analysis the VCXO. Then analyses the relationship between loop filter and phase noise. The low noise phase-locked oscillator consists of four parts:the static voltage circuit, VCXO circuit, temperature circuit and phase-locked loop. Each part has its special function, they work together to format the final design. The static voltage circuit provides static voltage for each module. VCXO provides good phase noise performance in remote of the signal. Voltage controlled circuit provides a constant temperature for VCXO. In this paper, use ADS to simulate the VCXO circuit, use ADS to simulate the phase-locked loop, proved it is feasibility from theory. Finally complete a series circuit debugging and testing, the test result shows us the phase noise indicators:-100dBc/Hz@10Hz,-120dBc/Hz@100Hz,-145dBc/Hz@lkHz,-155dBc/Hz@10kHz,-165dBc/Hz@100kHz, achieved the low noise requirement.