线性调频信号+高斯白噪声 怎么写

信号加高斯白噪声，然后通过匹配滤波器，再对信号检测的代码怎么写啊？

http://www.mathworks.com/help/phased/ug/matched-filtering.html

% Specify the waveform.hwav = phased.LinearFMWaveform('PulseWidth',1e-4,'PRF',5e3,...  'SampleRate',1e6,'OutputFormat','Pulses','NumPulses',1,...  'SweepBandwidth',1e5);w = getMatchedFilter(hwav);% Create a matched filter with no spectrum weighting, and a% matched filter that uses a Taylor window for spectrum% weighting.hmf = phased.MatchedFilter('Coefficients',w);hmf_taylor = phased.MatchedFilter('Coefficients',w,...  'SpectrumWindow','Taylor');% Create the signal and add noise.sig = step(hwav);rng(17)x = sig+0.5*(randn(length(sig),1)+1j*randn(length(sig),1));% Filter the noisy signal separately with each of the filters.y = step(hmf,x);y_taylor = step(hmf_taylor,x);% Plot the real parts of the waveform and noisy signal.t = linspace(0,numel(sig)/hwav.SampleRate,...  hwav.SampleRate/hwav.PRF);subplot(2,1,1);plot(t,real(sig)); title('Input Signal');xlim([0 max(t)]); grid onylabel('Amplitude');subplot(2,1,2);plot(t,real(x)); title('Input Signal + Noise');xlim([0 max(t)]); grid onxlabel('Seconds'); ylabel('Amplitude');% Plot the magnitudes of the two matched filter outputs.figure;plot(t,abs(y),'b--');title('Matched Filter Output');xlim([0 max(t)]); grid onhold on;plot(t,abs(y_taylor),'r-');ylabel('Magnitude'); xlabel('Seconds');legend('No Spectrum Weighting','Taylor Window');hold off;这是你给我的答案，我把它截出来了，还有个问题，如果我想改噪声的信噪比，要怎么改啊

x = sig+0.5*(randn(length(sig),1)+1j*randn(length(sig),1));0.5改成相应的（噪声功率/2）

就是把0.5改成小于1的其他数就可以是吧，还有一个问题，大神，老师让我“给线性调频信号加噪声，然后通过匹配滤波器，然后检测该信号”。这个函数写到了通过匹配滤波器了，最后一步的检测怎么写啊x = sig+0.5*(randn(length(sig),1)+1j*randn(length(sig),1));这个噪声时什么噪声，是高斯白噪声吗问题有点多，不好意思啊

改成合适的数。0.5对应的是噪声功率为1，至于你的噪声功率应该是多少要根据你的信号功率以及信噪比来求。

randn指normal分布，也就是高斯分布，所以是高斯白噪声。你想怎么检测？你觉得应该写成啥样？比如x>5就是一种检测