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我想计算噪声信号和滤波信号的SNR。我使用了下面的代码,但我不确定结果是否正确。有人能帮助我吗?如何在Matlab中计算信号的信噪比?
%generate the noisy signal which will be filtered
x= cos(2*pi*12*[0:0.001:1.23]);
x(end) = [];
[b,a] = butter(2,[0.6 0.7],'bandpass');
filtered_noise = filter(b,a,randn(1, length(x)*2));
y = (x + 0.5*filtered_noise(500:500+length(x)-1))/length(x)*2;
%Use matlabs built-in buttord function to get the optimum order to meet a
specification
[N,Wn] = buttord(0.1, 0.5, 5, 40)
%use the N and Wn values obtained above to design the filter in the usual
way
[b,a] = butter(N, Wn, 'low');
%filter the signal and plot the ouput of the filter
Y_filtered = filter(b,a,y);
%calculation of snr before filtering
snr_before = mean(x.^2)/mean(filtered_noise.^2);
snr_before_db = 10 * log10(snr_before) % in dB
%calculation of snr after filtering
residual_noise = x - Y_filtered;
snr_after = mean(x.^2)/mean(residual_noise.^2);
snr_after_db = 10 * log10(snr_after)
结果,我得到的是:
snr_before_db =
6.8725
snr_after_db =
0.0132
好吧。那么,如何在滤波之前知道SNR的值?以便我可以比较不同类型的过滤器之间的结果。 – Alisa