The Design And Realization Of The HF Hopping Synthesizer

This thesis is supported by the development process of one kind of high frequency (HF) digitization radio,so the thetis has important practical significance and broading application prospects. The HF radio not only accomplished the business functions such as digitalization of intermediate frequency (IF) signal, modulation and demodulation of baseband signal, digital voice and data, but also realized communication automation with the help of the digital signal processing (DSP). The application of the third generation of HF adaptive frequency hopping communication system (3G-ALE) make the radio hopping in sub-band in HF range, which improves the anti-jamming ability and makes the encrypt digital voice and data come true, and guarantees the safety of the transmission information.To realize anti-jamming capability, the design of frequency synthesizer in the thesis is the key part of the frequency hopping radio. In a word, the carrier frequency of the radio changes with the the first local oscillator, so the frequency synthesizer plays an important role in the performances of HF radio.Starting with the problems existing in products which adopted the frequency synthesizer, The thesis analyze the problems of the freguency spectrum source by resolving the measuring results including the frequency spectrum, phase noise,and the specific data of the spurious signals. Based on the original plan, The thesis summarizes the improving measurement of the spurious and phase noise and provide the results of comparison. Thus we present the DDS+PLL mixing frequency synthesizer to achieve a new kind of frequency synthesizer with high -stability, low-cost, low phase noise, low spurious, high resolution ratio and required frequency hopping time.Compared with the applied frequency synthesizer, we take full advantage of the independence of the fist and the second local oscillator to avoid the interference; We also improve the requirements of the chips such as VCO, TCXO, DDS and 2nd PLL chip; What's more, we adopt four layers PCB with independent ground layer, and strengthen shielding measures to further increase the circuit. For the choice of phase comparison frequency and loop bandwidth, we try to narrow loop bandwidth and improve the design of phase frequency based on not affecting the required frequency hopping time; As to the low price, we take off the charge pump booster circuits. Also, we use a piece of PLL chip instead of the original 2nd phase-locked loop and independent charge pump circuit chip.After components selection, circuit design, PCB typesetting,simulation experiment,adjustment experiment,result measurement and analysis,a kind of best frequency synthesizer unit which satisfies the technical requirement of one type of HF digitalization radio is implemented.