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为了保证测速和测距精度,有效手段之一是在星载统一测控应答机上采用嵌套环路结构的载波跟踪环完成相干载波提取。由于利用了相干本振补偿多普勒频移,必须考虑输入相位噪声对本振相位噪声的影响。为了准确预测环路输出相位噪声性能,对环路中各部件贡献的相位噪声进行了分析。针对不同噪声源,运用信号流图的分析方法建立了对应的环路相位噪声模型,通过仿真计算得到了不同输入信号功率条件下的环路输出相位噪声功率谱,与实际电路的测试结果对比,证明了该环路相位噪声模型的准确性。应用该模型能提高环路设计的准确性和效率。
In order to ensure the accuracy of speed measurement and ranging, one of the effective means is to use the carrier tracking loop of the nested loop structure to complete the coherent carrier extraction on the unified monitoring and control transponder of the satellite. Due to the use of coherent LO compensation Doppler shift, we must consider the input phase noise on LO phase noise. In order to accurately predict the phase-to-phase noise performance of the loop output, the contribution of phase noise to the various components in the loop is analyzed. For different noise sources, the corresponding phase noise model of the loop is established by using the method of signal flow graph. The phase noise power spectrum of the loop output under different input signal power conditions is simulated. Compared with the test results of the actual circuit, The accuracy of the loop phase noise model is proved. The application of this model can improve the accuracy and efficiency of loop design.