scipy.signal.bode(system, w=None, n=100)[source]

Calculate Bode magnitude and phase data of a continuous-time system.


system : an instance of the LTI class or a tuple describing the system.

The following gives the number of elements in the tuple and the interpretation:

  • 1 (instance of lti)
  • 2 (num, den)
  • 3 (zeros, poles, gain)
  • 4 (A, B, C, D)

w : array_like, optional

Array of frequencies (in rad/s). Magnitude and phase data is calculated for every value in this array. If not given a reasonable set will be calculated.

n : int, optional

Number of frequency points to compute if w is not given. The n frequencies are logarithmically spaced in an interval chosen to include the influence of the poles and zeros of the system.


w : 1D ndarray

Frequency array [rad/s]

mag : 1D ndarray

Magnitude array [dB]

phase : 1D ndarray

Phase array [deg]


If (num, den) is passed in for system, coefficients for both the numerator and denominator should be specified in descending exponent order (e.g. s^2 + 3s + 5 would be represented as [1, 3, 5]).

New in version 0.11.0.


>>> from scipy import signal
>>> import matplotlib.pyplot as plt
>>> sys = signal.TransferFunction([1], [1, 1])
>>> w, mag, phase = signal.bode(sys)
>>> plt.figure()
>>> plt.semilogx(w, mag)    # Bode magnitude plot
>>> plt.figure()
>>> plt.semilogx(w, phase)  # Bode phase plot

(Source code)


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