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ADD: only frequency correction method to the PLL #24

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ADD: only frequency correction method to the PLL #24

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31 changes: 31 additions & 0 deletions scripts/pll.py
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Original file line number Diff line number Diff line change
Expand Up @@ -75,6 +75,37 @@ def correct_phase_offset(self):
self.phase_list = np.append(self.phase_list, phase)


def correct_frequency_offset(self):
""" Use P control to estimate frequency offset in self.data, correct for
it, and save the corrected data as self.data_fixed. """

freq = 0
err = 0

self.data_fixed = np.array([])

self.abs_val_list = np.array([])
self.err_list = np.array([])
self.freq_list = np.array([])

for i, x in enumerate(self.data):

# Multiply input value by complex exponential of specified phase
y = x * np.exp(-freq * i * j)
self.data_fixed = np.append(self.data_fixed, y)

# Estimate error in phase for BPSK
err = y.real * y.imag

# Use PID control to find the phase offset for the next step
freq += self.k_p * err

# Track data for plottting
self.err_list = np.append(self.err_list, err)
self.abs_val_list = np.append(self.abs_val_list, np.absolute(x))
self.freq_list = np.append(self.freq_list, freq)


def plot_data(self):
""" Visualize! """

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