FilterDesign.py 文件源码

def butterplot(fs,fc):
    """
    https://docs.scipy.org/doc/scipy/reference/generated/scipy.signal.butter.html
    """
    b, a = signal.butter(4, 100, 'low', analog=True)
    w, h = signal.freqs(b, a)
    ax = figure().gca()
    ax.semilogx(fs*0.5/np.pi*w, 20*np.log10(abs(h)))
    ax.set_title('Butterworth filter frequency response')
    ax.set_xlabel('Frequency [Hz]')
    ax.set_ylabel('Amplitude [dB]')
    ax.grid(which='both', axis='both')
    ax.axvline(fc, color='green') # cutoff frequency
    ax.set_ylim(-50,0)