iirnotch(w0, Q, fs=2.0)
A notch filter is a band-stop filter with a narrow bandwidth (high quality factor). It rejects a narrow frequency band and leaves the rest of the spectrum little changed.
Frequency to remove from a signal. If :None:None:`fs` is specified, this is in the same units as :None:None:`fs`. By default, it is a normalized scalar that must satisfy 0 < w0 < 1
, with w0 = 1
corresponding to half of the sampling frequency.
Quality factor. Dimensionless parameter that characterizes notch filter -3 dB bandwidth bw
relative to its center frequency, Q = w0/bw
.
The sampling frequency of the digital system.
Numerator ( b
) and denominator ( a
) polynomials of the IIR filter.
Design second-order IIR notch digital filter.
Design and plot filter to remove the 60 Hz component from a signal sampled at 200 Hz, using a quality factor Q = 30
>>> from scipy import signal
... import matplotlib.pyplot as plt
>>> fs = 200.0 # Sample frequency (Hz)
... f0 = 60.0 # Frequency to be removed from signal (Hz)
... Q = 30.0 # Quality factor
... # Design notch filter
... b, a = signal.iirnotch(f0, Q, fs)
>>> # Frequency response
... freq, h = signal.freqz(b, a, fs=fs)
... # Plot
... fig, ax = plt.subplots(2, 1, figsize=(8, 6))
... ax[0].plot(freq, 20*np.log10(abs(h)), color='blue')
... ax[0].set_title("Frequency Response")
... ax[0].set_ylabel("Amplitude (dB)", color='blue')
... ax[0].set_xlim([0, 100])
... ax[0].set_ylim([-25, 10])
... ax[0].grid()
... ax[1].plot(freq, np.unwrap(np.angle(h))*180/np.pi, color='green')
... ax[1].set_ylabel("Angle (degrees)", color='green')
... ax[1].set_xlabel("Frequency (Hz)")
... ax[1].set_xlim([0, 100])
... ax[1].set_yticks([-90, -60, -30, 0, 30, 60, 90])
... ax[1].set_ylim([-90, 90])
... ax[1].grid()
... plt.show()
The following pages refer to to this document either explicitly or contain code examples using this.
scipy.signal._filter_design.iirnotch
scipy.signal._filter_design.iircomb
scipy.signal._filter_design.iirpeak
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