Add tests for ambiguity functions

tftb/processing/tests/test_ambiguity.py

@@ -0,0 +1,72 @@
+#! /usr/bin/env python
+# -*- coding: utf-8 -*-
+# vim:fenc=utf-8
+#
+# Cube26 product code
+#
+# (C) Copyright 2015 Cube26 Software Pvt Ltd
+# All right reserved.
+#
+# This file is confidential and NOT open source.  Do not distribute.
+#
+
+"""
+Tests for tftb.processing.ambiguity
+"""
+
+import unittest
+import numpy as np
+
+from tftb.generators import fmlin, amgauss, altes
+from tftb.processing import ambiguity
+from tftb.tests.base import TestBase
+
+
+class TestWideBand(TestBase):
+    """Tests for the wide band ambiguity function."""
+    def setUp(self):
+        self.signal = altes(128, 0.1, 0.45)
+        self.tfr, self.tau, self.theta = ambiguity.wide_band(self.signal)
+
+    def test_max_value(self):
+        """Test if the maximum value of the ambiguity function occurs at the
+        origin"""
+        max_ix = np.argmax(np.abs(self.tfr))
+        self.assertAlmostEqual(float(self.tfr.size) / max_ix, 2, places=1)
+
+
+class TestNarrowBand(TestBase):
+    """Tests for the narrow band ambiguity function"""
+
+    def setUp(self):
+        x = fmlin(64, 0.2, 0.5)[0] * amgauss(64)
+        y = fmlin(64, 0.3, 0)[0] * amgauss(64)
+        self.signal = np.hstack((x, y))
+        self.tfr, self.lag, self.doppler = ambiguity.narrow_band(self.signal)
+
+    def test_max_value(self):
+        """Test if the maximum value of the ambiguity function occurs at the
+        origin"""
+        xorg, yorg = map(lambda x: x / 2, self.tfr.shape)
+        abs_mat = np.abs(self.tfr) ** 2
+        max_val = abs_mat[xorg, yorg]
+        for i in range(abs_mat.shape[0]):
+            for j in range(abs_mat.shape[1]):
+                self.assertTrue(abs_mat[i, j] <= max_val)
+
+    def test_volume_invariance(self):
+        """Test the volume invariance property of the narrow band ambiguity
+        function."""
+        volume = np.abs(self.tfr[self.doppler == 0, self.lag == 0]) ** 2
+        volume_integral = (np.abs(self.tfr) ** 2).sum().sum()
+        self.assertAlmostEqual(volume[0],
+                               volume_integral / (self.signal.shape[0] / 2))
+
+    @unittest.skip("Not quite ready yet.")
+    def test_symmetry(self):
+        """Test the symmetry property of the narrow band ambiguity function."""
+        tfr = self.tfr[1:, :]
+        self.assert_is_hermitian(tfr)
+
+if __name__ == '__main__':
+    unittest.main()

tftb/tests/base.py

@@ -61,3 +61,8 @@ def assert_is_monotonic_decreasing(self, signal):
         derivative = np.diff(signal)
         if not np.all(derivative <= 0):
             raise AssertionError("Signal is not monotonically decreasing.")
+
+    def assert_is_hermitian(self, x):
+        """Assert that the input is a Hermitian matrix."""
+        conj_trans = np.conj(x).T
+        np.testing.assert_allclose(x, conj_trans)