Research On Low Phase Noise Frequency Synthesizer At S-band

The frequency synthesis technology plays an extremely important role in the RF and microwave systems. In recent years with the continuous development in the aerospace, communications, radar and telemetry, they put forward new requirements for frequency synthesis technology. They demand that the output of frequency synthesizer should have better index in all aspects such as the output range, stability, spectral purity, hopping speed, etc.This thesis introduced the history development and current status of frequency synthesis technology. Advantages and disadvantages of several existing schemes in frequency synthesis technology were given based on analysis. Then a new scheme was introduced. The low noise mixer PLL structure in the new scheme could greatly improve the phase noise and brought no deterioration in spurious performance at the same time. The feasibility of the whole scheme was verified by the calculation of the indicators.A 2GHz~5GHz frequency synthesizer based on a broadband YTO with 1kHz resolution was designed. The SSB phase noise of the synthesizer at 5GHz was-99dBc/Hz@10kHz. The synthesizer is composed of reference module, main-loop module, YTO module, control module and power supply module. The control module communicates with other modules through the SPI bus. The frequency synthesizer can be controlled by the keyboard on itself or a PC connected by USB.