python - 如何获取并绘制信号包络线

Question

我想知道Python中是否有一个函数envelope可以得到与此相同的结果

我已经在 Python 中尝试过 envelope 函数，但有这个结果，它与我想要的不符。

Answer 1

虽然您没有具体提及您使用的功能，但似乎您正在使用两种不同类型的信封。

matlab中调用envelope的方式，相关描述为:

[yupper,ylower] = envelope(x) returns the upper and lower envelopes of the input sequence, x, as the magnitude of its analytic signal. The analytic signal of x is found using the discrete Fourier transform as implemented in hilbert. The function initially removes the mean of x and adds it back after computing the envelopes. If x is a matrix, then envelope operates independently over each column of x.

基于此，我想您会寻找一种在 python 中获得希尔伯变换的方法。可以找到这样的示例 here :

 import numpy as np
 import matplotlib.pyplot as plt
 from scipy.signal import hilbert, chirp

 duration = 1.0
 fs = 400.0
 samples = int(fs*duration)
 t = np.arange(samples) / fs

 signal = chirp(t, 20.0, t[-1], 100.0)
 signal *= (1.0 + 0.5 * np.sin(2.0*np.pi*3.0*t) )

 analytic_signal = hilbert(signal)
 amplitude_envelope = np.abs(analytic_signal)
 instantaneous_phase = np.unwrap(np.angle(analytic_signal))
 instantaneous_frequency = np.diff(instantaneous_phase) / (2.0*np.pi) * fs

 fig = plt.figure()
 ax0 = fig.add_subplot(211)
 ax0.plot(t, signal, label='signal')
 ax0.plot(t, amplitude_envelope, label='envelope')
 ax0.set_xlabel("time in seconds")
 ax0.legend()
 ax1 = fig.add_subplot(212)
 ax1.plot(t[1:], instantaneous_frequency)
 ax1.set_xlabel("time in seconds")
 ax1.set_ylim(0.0, 120.0)

结果: