摘要
本文提出一种采用双通道前放的互功率谱估计方法。对互谱周期图估计的偏量及方差计算表明,互谱估计的期望值可以消除前放噪声及零漂等影响,从而保证了微弱信号功率谱的准确测量。文中指出,前放噪声会加大互谱估计的方差,并引起幅值估计的附加偏量,因此采用低噪声前放及平滑周期图平均法仍是十分必要的。用本方法对低于前放噪声一个数量级的小电阻热噪声及二极管PN结电流散弹噪声功率谱进行了测量,测量结果与理论值基本一致。
A double-channel preamplifier cross correlation measurement method is proposed.Theoretical analysis shows that the expected value of the cross spectral density is incoherent with the noise and zero-drift of the preamplifier.Consequently,this method can ensure the accurate measurement of weak random signals.It is also found that the noise of the preamplifier may increase the variance of the periodgram of the cross spectral density and cause an additional bias of the cross spectrum estimation.Hence,the average periodgram using windowing procedures and low noise preamplifier are necessary for the cross power spectrum estimation.Finally,the thermal noise of a small resistor and the shot noise of a p-n junction are measured.Experimental results are in good agreement with the theoretical values.It means that this method is feasible and accurate for the spectrum measurement of weak random signals even at a S/N ratio of less than 1/10.
出处
《计量学报》
CSCD
1991年第4期306-315,共10页
Acta Metrologica Sinica
