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gri_mmse_fir_interpolator_cc.h
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1 /* -*- c++ -*- */
2 /*
3  * Copyright 2002,2007 Free Software Foundation, Inc.
4  *
5  * This file is part of GNU Radio
6  *
7  * GNU Radio is free software; you can redistribute it and/or modify
8  * it under the terms of the GNU General Public License as published by
9  * the Free Software Foundation; either version 3, or (at your option)
10  * any later version.
11  *
12  * GNU Radio is distributed in the hope that it will be useful,
13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15  * GNU General Public License for more details.
16  *
17  * You should have received a copy of the GNU General Public License
18  * along with GNU Radio; see the file COPYING. If not, write to
19  * the Free Software Foundation, Inc., 51 Franklin Street,
20  * Boston, MA 02110-1301, USA.
21  */
22 #ifndef _GRI_MMSE_FIR_INTERPOLATOR_CC_H_
23 #define _GRI_MMSE_FIR_INTERPOLATOR_CC_H_
24 
25 #include <gr_core_api.h>
26 #include <gr_complex.h>
27 #include <vector>
28 
29 class gr_fir_ccf;
30 
31 /*!
32  * \brief Compute intermediate samples between signal samples x(k*Ts)
33  * \ingroup filter_primitive
34  *
35  * This implements a Mininum Mean Squared Error interpolator with 8 taps.
36  * It is suitable for signals where the bandwidth of interest B = 1/(4*Ts)
37  * Where Ts is the time between samples.
38  *
39  * Although mu, the fractional delay, is specified as a float, it is actually
40  * quantized. 0.0 <= mu <= 1.0. That is, mu is quantized in the interpolate
41  * method to 32nd's of a sample.
42  *
43  * For more information, in the GNU Radio source code, see:
44  * \li gnuradio-core/src/gen_interpolator_taps/README
45  * \li gnuradio-core/src/gen_interpolator_taps/praxis.txt
46  */
47 
49 public:
52 
53  unsigned ntaps () const;
54  unsigned nsteps () const;
55 
56  /*!
57  * \brief compute a single interpolated output value.
58  *
59  * \p input must have ntaps() valid entries and be 8-byte aligned.
60  * input[0] .. input[ntaps() - 1] are referenced to compute the output value.
61  * \throws std::invalid_argument if input is not 8-byte aligned.
62  *
63  * \p mu must be in the range [0, 1] and specifies the fractional delay.
64  *
65  * \returns the interpolated input value.
66  */
67  gr_complex interpolate (const gr_complex input[], float mu);
68 
69 protected:
70  std::vector<gr_fir_ccf *> filters;
71 };
72 
73 
74 #endif /* _GRI_MMSE_FIR_INTERPOLATOR_CC_H_ */