GNU Radio Manual and C++ API Reference 3.8.5.0
The Free & Open Software Radio Ecosystem
 
Loading...
Searching...
No Matches
fft_shift.h
Go to the documentation of this file.
1/* -*- c++ -*- */
2/*
3 * Copyright 2019 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
23#ifndef INCLUDED_FFT_FFT_SHIFT_H
24#define INCLUDED_FFT_FFT_SHIFT_H
25
26#include <algorithm>
27#include <cassert>
28#include <vector>
29
30namespace gr {
31namespace fft {
32
33/*! \brief reorder FFT results which are ordered from 0 to 1 in normalized frequency
34 * to -0.5 to 0.5 by cyclic shift
35 */
36template <typename T>
38{
39public:
40 fft_shift(size_t fft_length)
41 : d_fftlen(fft_length),
42 d_lenpos(fft_length / 2 + (fft_length % 2)),
43 d_lenneg(fft_length / 2),
44 d_buf(fft_length)
45 {
46 }
47
48 /*! performs the cyclic shift on a vector v
49 */
50 void shift(std::vector<T>& v) { shift(&v.front(), v.size()); }
51
52 /*! performs the cyclic shift on an array
53 */
54 void shift(T* data, size_t fft_len)
55 {
56 resize(fft_len);
57 std::copy_n(data, d_lenpos, d_buf.begin());
58 std::copy_n(data + d_lenpos, d_lenneg, data);
59 std::copy_n(d_buf.begin(), d_lenpos, data + d_lenneg);
60 }
61
62 /*! if needed adjusts the buffer size to a new fft length
63 */
64 void resize(size_t fft_length)
65 {
66 if (d_fftlen == fft_length)
67 return;
68 d_fftlen = fft_length;
69 d_lenpos = d_fftlen / 2 + (d_fftlen % 2);
70 d_lenneg = d_fftlen / 2;
71 assert(d_lenpos + d_lenneg == d_fftlen);
72 d_buf.resize(d_lenpos);
73 }
74
75protected:
76private:
77 size_t d_fftlen; // FFT length
78 size_t d_lenpos; // number of FFT bins with positive frequencies
79 size_t d_lenneg; // number of FFT bins with negative frequencies
80 std::vector<T> d_buf; // buffer used for cyclic shift
81};
82
83} // namespace fft
84} // namespace gr
85#endif // INCLUDED_FFT_FFT_SHIFT_H
reorder FFT results which are ordered from 0 to 1 in normalized frequency to -0.5 to 0....
Definition fft_shift.h:38
fft_shift(size_t fft_length)
Definition fft_shift.h:40
void resize(size_t fft_length)
Definition fft_shift.h:64
void shift(std::vector< T > &v)
Definition fft_shift.h:50
void shift(T *data, size_t fft_len)
Definition fft_shift.h:54
GNU Radio logging wrapper for log4cpp library (C++ port of log4j)
Definition basic_block.h:46
Definition cc_common.h:45