Python implementation of wideband ambiguity function

ambiguity.py

# this is a python version of the wideband ambiguity function. A matlab version that it was ported from is below.
# https://dsp.stackexchange.com/questions/51372/how-to-calculate-the-ambiguity-function

import numpy as np
from scipy.interpolate import interp1d
from matplotlib import pylab as plt

tb = -1
tend = 1
dilation = 0.8

signal = np.zeros( 400,dtype = np.complex64 )
signal[100:300] = np.exp( 1J * 2 * np.pi * ( 4 * np.arange(200) + 0.01 * np.arange(200)**2 )/200 )

conj_rev_signal = np.conj( signal[::-1] )
time = np.linspace( tb, tend, len(signal) )
delay_time = np.linspace( 2*tb, 2*tend, 2*len(signal)-1 )
tau = np.linspace( dilation, 1./dilation, 512 )
out = np.zeros( [len(tau), 2*len(signal) -1] , dtype = np.complex64)

f = interp1d( time, conj_rev_signal, kind='cubic', fill_value='extrapolate' )
for i, t in enumerate(tau):
    out[i,:] = np.convolve( signal, f( time * t ) )

plt.figure(); plt.pcolor( delay_time, tau, np.abs(out) )