3 * Copyright 2002 Free Software Foundation, Inc.
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23 #include <atsci_root_raised_cosine_bandpass.h>
33 atsc_root_raised_cosine_bandpass::taps (double sampling_freq)
36 vector<float> t = atsc_root_raised_cosine::taps (sampling_freq);
38 cerr << "atsc_root_raised_cosine_bandpass::taps -- " << t.size () << endl;
40 // heterodyne the low pass coefficients up to the specified bandpass
41 // center frequency. Note that when we do this, the filter bandwidth
42 // is effectively twice the low pass (2.69 * 2 = 5.38) and hence
43 // matches the diagram in the ATSC spec.
45 double arg = 2 * M_PI * _center_freq / sampling_freq;
46 for (unsigned int i = 0; i < t.size (); i++)
47 // the factor of 2 keeps the gain of the passband normalized to 1
48 t[i] *= 2 * cos (arg * (double) i);