diff options
Diffstat (limited to 'dpd/src/Symbol_align.py')
| -rw-r--r-- | dpd/src/Symbol_align.py | 67 |
1 files changed, 36 insertions, 31 deletions
diff --git a/dpd/src/Symbol_align.py b/dpd/src/Symbol_align.py index e21e793..4ea79c5 100644 --- a/dpd/src/Symbol_align.py +++ b/dpd/src/Symbol_align.py @@ -1,6 +1,6 @@ # -*- coding: utf-8 -*- # -# Modulation Error Rate +# DPD Calculation Engine, Modulation Error Rate. # # http://www.opendigitalradio.org # Licence: The MIT License, see notice at the end of this file @@ -8,24 +8,50 @@ import datetime import os import logging -import time + try: logging_path = os.path.dirname(logging.getLoggerClass().root.handlers[0].baseFilename) except: logging_path = "/tmp/" import numpy as np -import src.Const import scipy import matplotlib + matplotlib.use('agg') import matplotlib.pyplot as plt + +def _remove_outliers(x, stds=5): + deviation_from_mean = np.abs(x - np.mean(x)) + inlier_idxs = deviation_from_mean < stds * np.std(x) + x = x[inlier_idxs] + return x + + +def _calc_delta_angle(fft): + # Introduce invariance against carrier + angles = np.angle(fft) % (np.pi / 2.) + + # Calculate Angle difference and compensate jumps + deltas_angle = np.diff(angles) + deltas_angle[deltas_angle > np.pi / 4.] = \ + deltas_angle[deltas_angle > np.pi / 4.] - np.pi / 2. + deltas_angle[-deltas_angle > np.pi / 4.] = \ + deltas_angle[-deltas_angle > np.pi / 4.] + np.pi / 2. + deltas_angle = _remove_outliers(deltas_angle) + + delta_angle = np.mean(deltas_angle) + + return delta_angle + + class Symbol_align: """ Find the phase offset to the start of the DAB symbols in an unaligned dab signal. """ + def __init__(self, c, plot=False): self.c = c self.plot = plot @@ -95,8 +121,8 @@ class Symbol_align: ax.set_title("Min Filter") ax = fig.add_subplot(4, 1, 4) - tx_product_crop = tx_product[peaks[0]-50:peaks[0]+50] - x = range(tx_product.shape[0])[peaks[0]-50:peaks[0]+50] + tx_product_crop = tx_product[peaks[0] - 50:peaks[0] + 50] + x = range(tx_product.shape[0])[peaks[0] - 50:peaks[0] + 50] ax.plot(x, tx_product_crop) ylim = ax.get_ylim() ax.plot((peaks[0], peaks[0]), (ylim[0], ylim[1])) @@ -113,38 +139,16 @@ class Symbol_align: # of the shift to find the offset of the symbol start. return (offset + self.c.T_C) % self.c.T_S - def _remove_outliers(self, x, stds=5): - deviation_from_mean = np.abs(x - np.mean(x)) - inlier_idxs = deviation_from_mean < stds * np.std(x) - x = x[inlier_idxs] - return x - - def _calc_delta_angle(self, fft): - # Introduce invariance against carrier - angles = np.angle(fft) % (np.pi / 2.) - - # Calculate Angle difference and compensate jumps - deltas_angle = np.diff(angles) - deltas_angle[deltas_angle > np.pi/4.] =\ - deltas_angle[deltas_angle > np.pi/4.] - np.pi/2. - deltas_angle[-deltas_angle > np.pi/4.] = \ - deltas_angle[-deltas_angle > np.pi/4.] + np.pi/2. - deltas_angle = self._remove_outliers(deltas_angle) - - delta_angle = np.mean(deltas_angle) - - return delta_angle - def _delta_angle_to_samples(self, angle): return - angle / self.c.phase_offset_per_sample - def _calc_sample_offset(self, sig, debug=False): - assert sig.shape[0] == self.c.T_U,\ + def _calc_sample_offset(self, sig): + assert sig.shape[0] == self.c.T_U, \ "Input length is not a Symbol without cyclic prefix" fft = np.fft.fftshift(np.fft.fft(sig)) fft_crop = np.delete(fft[self.c.FFT_start:self.c.FFT_end], self.c.FFT_delete) - delta_angle = self._calc_delta_angle(fft_crop) + delta_angle = _calc_delta_angle(fft_crop) delta_sample = self._delta_angle_to_samples(delta_angle) delta_sample_int = np.round(delta_sample).astype(int) error = np.abs(delta_sample_int - delta_sample) @@ -154,6 +158,7 @@ class Symbol_align: return delta_sample_int def calc_offset(self, tx): + """Calculate the offset the first symbol""" off_sym = self._calc_offset_to_first_symbol_without_prefix( tx) off_sam = self._calc_sample_offset( @@ -168,7 +173,7 @@ class Symbol_align: off = self.calc_offset(tx) return tx[ off: - off+self.c.T_U + off + self.c.T_U ] # The MIT License (MIT) |