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介绍了调制频率偏移抖动的起因,并分析了相干检测过程中由于调制频率偏移抖动所引起的误差,对模拟和数字相干调制和解调过程建立了数学模型。基于文中所建立的数学模型,确定了调制频率偏移抖动对模拟和数字相干调制和解调过程的影响,特别是其对离散采样过程的影响关系。最后,提出了一种基于模糊逻辑的隶属函数加权采样算法,并进行了实验。实验结果表明,使用隶属函数加权采样算法后,当调制频率偏移范围小于±9.2%时,相干检测的精度未受影响;而未使用隶属函数加权采样算法时,当调制频率偏移范围大于±3%时,相干检测的精度便会受到影响。结果还表明,调制频率偏移抖动对模拟和数字相干检测过程影响的数学模型在相干检测应用领域很有价值,提出的隶属函数加权采样算法能够有效地消除调制频率偏移对相干检测的影响,其效果已经在应用中得到了验证。
The causes of the modulation frequency offset jitter are introduced. The errors caused by the modulation frequency offset jitter in the coherent detection process are analyzed. A mathematical model is established for the analog and digital coherent modulation and demodulation processes. Based on the mathematical model established in this paper, the influence of modulation frequency offset jitter on the analog and digital coherent modulation and demodulation processes is determined, especially its influence on the discrete sampling process. Finally, a weighted sampling algorithm of membership function based on fuzzy logic is proposed and experiments are carried out. Experimental results show that the accuracy of coherent detection is not affected when the modulation frequency offset range is less than ± 9.2% when using the weighted sampling algorithm of membership function. When the weighting algorithm of membership function is not used, when the modulation frequency offset range is greater than ± 3%, the accuracy of coherent detection will be affected. The results also show that the mathematical model of modulation frequency offset jitter impact on the analog and digital coherent detection process is valuable in the field of coherent detection applications. The proposed membership function weighted sampling algorithm can effectively eliminate the impact of modulation frequency offset on coherent detection, Its effect has been verified in the application.