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本文以航天运载器为例分析了实测信号功率谱的低频畸变(所谓“低频上翘”)现象。指出造成低频畸变的原因是帧平均型数字谱分析限制、分辨率太低和样本长度不够。提出了功率谱分析中“可信分析频带”的概念。认为一次分析中的上下限频率之比必须小于40～50;或者,最低分析频率应大于分辨率的8～10倍。凡不满足上述条件的处理结果,低频段的功率谱密度值都是值得怀疑的。文中讨论了纠正低频畸变的方法。
In this paper, we take the space vehicle as an example to analyze the phenomenon of low frequency distortion (the so-called “low frequency upturned”) of the measured signal power spectrum. It is pointed out that the cause of low frequency distortion is the limit of frame average digital spectrum analysis, the resolution is too low and the sample length is not enough. Proposed the concept of “credible analysis frequency band” in power spectrum analysis. It is considered that the ratio between the upper and lower limit frequencies in an analysis must be less than 40-50; or the minimum analysis frequency should be greater than 8-10 times of the resolution. Those who do not meet the above conditions, the results of low-frequency power spectral density values are questionable. The paper discusses the method of correcting low frequency distortion.