Frequency-swept cosine generator, with a time-dependent frequency.
This function generates a sinusoidal function whose instantaneous frequency varies with time. The frequency at time t is given by the polynomial poly.
t : ndarray
poly : 1-D array-like or instance of numpy.poly1d
phi : float, optional
sweep_poly : ndarray
New in version 0.8.0.
If poly is a list or ndarray of length n, then the elements of poly are the coefficients of the polynomial, and the instantaneous frequency is:
f(t) = poly*t**(n-1) + poly*t**(n-2) + ... + poly[n-1]
If 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 phase is the integral from 0 to t of 2 * pi * f(t), f(t) as defined above.