Design And Implementation Of Fast Switching Frequency Synthesizer

Frequency synthesizer is widely used in the field of modern electronic system,which is called of the heart of the electronic system. With the development of electronic technology, the requirement on the indexes of the frequency synthesizer is higher and higher, frequency switching time as an important index has become a hot topic.YIG Tuned Oscillator(referred to YTO) is a microwave oscillator which uses a YIG sphere as the harmonic oscillator. Compared to VCO(voltage controlled oscillator),YTO can be made very wide tuning bandwidth, since YIG oscillators with high Q value, the phase noise performance is excellent, due to its linearity, wide tuning range, is widely applied to electronic counter measures, spectrum analyzers,microwave instruments jamming receivers as a local oscillator. Because of inductance of excitation coil and the eddy current effect of oscillation circuit, the YTO has hysteresis effect,affects the ability of fast frequency switching response. How to reduce the dynamic hysteresis effect so as to improve the tuning speed, is the key point of this thesis. In this thesis, YTO is used as the oscillator to achieve a wide band, low phase noise and fast switching frequency synthesizer.Firstly this thesis introduces the basic principle of frequency synthesis technology,including direct frequency synthesis technology, the phase-locked frequency synthesis technology, direct digital frequency synthesis technology, and gives the method of measuring the frequency switching time. Combine with the system indexes, the thesis adopts the hybrid DDS+PLL frequency synthesizer program. Through analyzing YTO circuit model and discussing the dynamic hysteresis of the YTO, the thesis builds the YTO response curve in step voltage. Finally, the thesis applies the program of controlling the tuning voltage in the frequency switching process, overcomes the dynamic hysteresis of the YTO and achieves fast frequency switching speed. By simulating and designing of the key circuit module, and using FPGA to realize the control of the system. Finally through debugging and testing of the circuit,meeting the requirements and achieving good compatibility.