sweep_poly(t, poly, phi=0)
This function generates a sinusoidal function whose instantaneous frequency varies with time. The frequency at time t is given by the polynomial :None:None:`poly`.
If :None:None:`poly` is a list or ndarray of length :None:None:`n`, then the elements of :None:None:`poly` are the coefficients of the polynomial, and the instantaneous frequency is:
f(t) = poly[0]*t**(n-1) + poly[1]*t**(n-2) + ... + poly[n-1]
If :None:None:`poly` is an instance of numpy.poly1d
, then the instantaneous frequency is:
f(t) = poly(t)
Finally, the output s is:
cos(phase + (pi/180)*phi)
where :None:None:`phase` is the integral from 0 to t of 2 * pi * f(t)
, f(t)
as defined above.
Times at which to evaluate the waveform.
The desired frequency expressed as a polynomial. If :None:None:`poly` is a list or ndarray of length n, then the elements of :None:None:`poly` are the coefficients of the polynomial, and the instantaneous frequency is
f(t) = poly[0]*t**(n-1) + poly[1]*t**(n-2) + ... + poly[n-1]
If :None:None:`poly` is an instance of numpy.poly1d, then the instantaneous frequency is
f(t) = poly(t)
Phase offset, in degrees, Default: 0.
A numpy array containing the signal evaluated at t with the requested time-varying frequency. More precisely, the function returns cos(phase + (pi/180)*phi)
, where :None:None:`phase` is the integral (from 0 to t) of 2 * pi * f(t)
; f(t)
is defined above.
Frequency-swept cosine generator, with a time-dependent frequency.
f(t) = 0.025*t**3 - 0.36*t**2 + 1.25*t + 2
over the interval 0 <= t <= 10.
>>> from scipy.signal import sweep_poly
... p = np.poly1d([0.025, -0.36, 1.25, 2.0])
... t = np.linspace(0, 10, 5001)
... w = sweep_poly(t, p)
Plot it:
>>> import matplotlib.pyplot as plt
... plt.subplot(2, 1, 1)
... plt.plot(t, w)
... plt.title("Sweep Poly\nwith frequency " +
... "$f(t) = 0.025t^3 - 0.36t^2 + 1.25t + 2$")
... plt.subplot(2, 1, 2)
... plt.plot(t, p(t), 'r', label='f(t)')
... plt.legend()
... plt.xlabel('t')
... plt.tight_layout()
... plt.show()
The following pages refer to to this document either explicitly or contain code examples using this.
scipy.signal._waveforms.sweep_poly
scipy.signal._waveforms._sweep_poly_phase
scipy.signal._waveforms.chirp
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