Python 如何在规定的信噪比下产生复杂的白噪声？

我使用以下代码生成具有指定SNR（信噪比）和零均值的复杂白噪声：

import numpy as np

def GenerateNoise(signal, SNR_dB): # desiredSNR [dB]; signal is an array with complex values
   n = np.zeros((len(signal),1), dtype=complex)
   # SNR = var_signal^2 / var_n^2
   snr = 10.0**(SNR_dB/10.0) # Desired linear SNR
   var_signal = signal.var() # Measure power of signal
   var_n = var_signal / snr # Calculate required noise power for desired SNR
   if (var_n == 0): # In case of a null signal
       var_n = snr
   e = np.random.normal(0, np.sqrt(var_n/2), size=(len(signal), 2)).view(np.complex) # Generate noise with calculated power
   for i in range(0, len(signal)):
        n[i,0] = n[i,0] + e[i][0]
   print(10.0*np.log10((np.var(signal)**2)/(np.var(n)**2)))
   return n

代码的灵感来自于此。问题是显示的SNR是指定SNR的两倍（例如，当SNR_dB=-10[dB]时，打印值为~-20[dB]）

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有人知道是什么错误吗？

我已经弄明白了。我没有计算，也没有正确显示噪音。这是更正后的代码，如果对任何人都有用：

import numpy as np
def GenerateNoise(signal, SNR_dB): # desiredSNR [dB]; signal is an array with complex values
   n = np.zeros((len(signal),1), dtype=complex)
   # SNR = var_signal / var_n
   snr = 10.0**(SNR_dB/10.0) # Desired linear SNR
   var_signal = signal.var() # Measure power of signal
   var_n = var_signal / snr # Calculate required noise power for desired SNR
   if (var_n == 0): # In case of a null signal
       var_n = snr
   e = np.random.normal(0, np.sqrt(var_n*2.0)/2.0, size=(len(signal), 2)).view(np.complex) # Generate noise with calculated power
   for i in range(0, len(signal)):
       n[i,0] = n[i,0] + e[i][0]
   print(10.0*np.log10((np.var(signal))/(np.var(n))))
   return n