From 7545f892a6d9555ff89381618fd2ece7f0420eaf Mon Sep 17 00:00:00 2001 From: "Matthias P. Braendli" Date: Sat, 4 Feb 2017 17:11:11 +0100 Subject: Add jupyter notebook about subsample delay experiments --- align/GenerateExampleTxRxIQ.ipynb | 1795 +++++++++++++++++++++++++++++++++++++ align/README.md | 3 + 2 files changed, 1798 insertions(+) create mode 100644 align/GenerateExampleTxRxIQ.ipynb create mode 100644 align/README.md (limited to 'align') diff --git a/align/GenerateExampleTxRxIQ.ipynb b/align/GenerateExampleTxRxIQ.ipynb new file mode 100644 index 0000000..8f2fe6b --- /dev/null +++ b/align/GenerateExampleTxRxIQ.ipynb @@ -0,0 +1,1795 @@ +{ + "cells": [ + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "# Generate an example RX and TX dataset, with a subsample delay and try to resolve it afterwards" + ] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "## Generate signal" + ] + }, + { + "cell_type": "code", + "execution_count": 12, + "metadata": { + "collapsed": false + }, + "outputs": [], + "source": [ + "%matplotlib notebook\n", + "\n", + "import matplotlib.pyplot as plt\n", + "import scipy.signal\n", + "import numpy as np\n", + "\n", + "\n", + "iq_file = \"/home/bram/dab/aux/odr-dab-cir/phasereference.2048000.fc64.iq\"\n", + "\n", + "iq_data = np.fromfile(iq_file, np.complex64)\n", + "phase_ref_iq = scipy.signal.resample(iq_data, 2 * len(iq_data))\n", + "\n", + "noise_iq = np.random.normal(scale = np.max(np.abs(phase_ref_iq)) * 0.02,\n", + " size=len(phase_ref_iq))\n", + "\n", + "phase_ref_iq = phase_ref_iq + noise_iq\n", + "\n", + "# exp(-2i pi f) is the Fourier transform of a unity delay.\n", + "# exp(2i pi f) is a negative delay.\n", + "bin_frequencies = np.concatenate(\n", + " (np.linspace(0, 0.5, len(phase_ref_iq)/2, endpoint=False),\n", + " np.linspace(-0.5, 0, len(phase_ref_iq)/2, endpoint=False)))\n", + "\n", + "phase_ref_uc = scipy.signal.resample(phase_ref_iq, 4 * len(phase_ref_iq))\n", + "\n", + "do_integer_compensation = 0\n", + "delay = 1\n", + "\n", + "phase_ref_uc_delayed = np.roll(phase_ref_uc, delay)\n", + "\n", + "phase_ref_delayed = scipy.signal.resample(phase_ref_uc_delayed, len(phase_ref_iq))" + ] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "## Part 1: integer delay" + ] + }, + { + "cell_type": "code", + "execution_count": 13, + "metadata": { + "collapsed": false, + "scrolled": false + }, + "outputs": [ + { + "name": "stdout", + "output_type": "stream", + "text": [ + "Integer delay corrected: 0\n" + ] + } + ], + "source": [ + "corr_begin_ix = -32\n", + "corr_end_ix = 32\n", + "\n", + "corr = [np.abs(np.corrcoef(phase_ref_delayed, np.roll(phase_ref_iq, i))[0,1]) \n", + " for i in range(corr_begin_ix, corr_end_ix)]\n", + "# TODO check for negative real correlation peak\n", + "if do_integer_compensation:\n", + " delay_in = np.argmax(corr) + corr_begin_ix\n", + "else:\n", + " delay_in = 0\n", + "\n", + "phase_ref_int_delay_removed = np.roll(phase_ref_delayed, -delay_in)\n", + "\n", + "print(\"Integer delay corrected: {}\".format(delay_in))" + ] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "## Part 2: factional delay" + ] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "### Calculate fractional delay" + ] + }, + { + "cell_type": "code", + "execution_count": 14, + "metadata": { + "collapsed": false, + "scrolled": false + }, + "outputs": [ + { + "name": "stdout", + "output_type": "stream", + "text": [ + "Applying subsample correction: -0.4999999999999981\n", + "-3249.30731816 5104.0 -1.0 0.0 0.0\n" + ] + }, + { + "data": { + "application/javascript": [ + "/* Put everything inside the global mpl namespace */\n", + "window.mpl = {};\n", + "\n", + "mpl.get_websocket_type = function() {\n", + " if (typeof(WebSocket) !== 'undefined') {\n", + " return WebSocket;\n", + " } else if (typeof(MozWebSocket) !== 'undefined') {\n", + " return MozWebSocket;\n", + " } else {\n", + " alert('Your browser does not have WebSocket support.' +\n", + " 'Please try Chrome, Safari or Firefox ≥ 6. 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