nr = np.array([1.0, 1.52, 1.0]) # real part ni = np.array([0.0, 0.015, 0.0]) # imaginary part (attenuation) n_layers = 1 # the number of layers in the structure d = np.array([0.1016]) # thickness of the layers in mm slice_loc = 400 # index which to remove front blip theta0 = 17.5 * np.pi / 180 # the incoming angle of the THz scanner in radians c = 0.2998 # speed of light in mm/ps n = nr - 1j * ni # make the complex n ref_file = 'C:\\Work\\Signal Modelling\\References\\ref 12JUN2017\\60 ps waveform.txt' sample_file = 'C:\\Work\\Signal Modelling\\THz Data\\HDPE Lens\\60 ps waveform.txt' ref_time, ref_amp = sm.read_reference_data(ref_file) time, sample_amp = sm.read_reference_data(sample_file) ref_time -= ref_time[0] # shift time so initial value is zero ref_amp[:slice_loc] = 0 ref_amp[slice_loc - 1] = ref_amp[slice_loc] / 2 # add ramp for FFT sample_amp[:slice_loc] = 0 sample_amp[slice_loc - 1] = sample_amp[slice_loc] / 2 dt = ref_time[-1] / (len(ref_time) - 1) df = 1 / (len(ref_time) * dt) freq = np.linspace(0, len(ref_time) / 2 * df, len(ref_time) // 22) # calculate theta in each angle theta = np.zeros(n_layers + 2, dtype=complex) theta[0] = theta0 # first theta is just the angle of the THz scanner
# indices to slice the waveform, gate the front and back surface echos # this removes the initial "blip" and cuts out the water vapor noise in the middle # produces a much smoother spectrum gate0 = 615 # list of colors to use for plotting colors = ['r', 'b', 'g', 'k', 'm', 'c', 'y'] # ============================================================================== # END SETTINGS # START PREPROCESSING extent = (ni_guess[0], ni_guess[-1], nr_guess[-1], nr_guess[0]) ref_time, ref_amp = sm.read_reference_data(ref_file) data = THzData.THzData(tvl_file, basedir, gate=thz_gate, follow_gate_on=True) # adjust time arrays so initial data point is zero ref_time -= ref_time[0] # assume both have the same dt dt = ref_time[-1] / (len(ref_time) - 1) df = 1 / (len(ref_time) * dt) freq = np.linspace(0, len(ref_time)/2*df, len(ref_time)//2+1) e0 = copy.deepcopy(ref_amp) # e0 will be the negative of reference from aluminum plate e0[:gate0] = 0 # make everything before cut index zero to remove blip e0[gate0-1] = e0[gate0] / 2 # add ramp up factor to help FFT e0_gated = copy.deepcopy(e0)