scipy.signal.dbode

scipy.signal.dbode(system, w=None, n=100)

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

Parameters:

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 dlti)
• 2 (num, den, dt)
• 3 (zeros, poles, gain, dt)
• 4 (A, B, C, D, dt)

w : array_like, optional

Array of frequencies (in radians/sample). 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.

Returns:

w : 1D ndarray

Frequency array [rad/time_unit]

mag : 1D ndarray

Magnitude array [dB]

phase : 1D ndarray

Phase array [deg]

Notes

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

New in version 0.18.0.

Examples

>>> from scipy import signal
>>> import matplotlib.pyplot as plt

Transfer function: H(z) = 1 / (z^2 + 2z + 3)

>>> sys = signal.TransferFunction([1], [1, 2, 3], dt=0.05)

Equivalent: sys.bode()

>>> w, mag, phase = signal.dbode(sys)

>>> plt.figure()
>>> plt.semilogx(w, mag)    # Bode magnitude plot
>>> plt.figure()
>>> plt.semilogx(w, phase)  # Bode phase plot
>>> plt.show()