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/*
* Copyright (C) 2003 by Jonathan Naylor G4KLX
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
#include "Hilbert.h"
#include <wx/log.h>
#include <wx/debug.h>
#include <cmath>
using namespace std;
const int FILTER_LEN = 37;
const int BUFFER_LEN = 1024;
/*
* Create a band pass Hilbert transformer / filter with 6 dB corner
* frequencies of 'f1' and 'f2'. (0 <= f1 < f2 <= 0.5)
*/
CHilbert::CHilbert(double f1, double f2) :
m_iFilter(NULL),
m_qFilter(NULL),
m_iBuffer(NULL),
m_qBuffer(NULL),
m_ptr(FILTER_LEN)
{
m_iFilter = new double[FILTER_LEN];
m_qFilter = new double[FILTER_LEN];
m_iBuffer = new double[BUFFER_LEN];
m_qBuffer = new double[BUFFER_LEN];
for (int i = 0; i < FILTER_LEN; i++) {
double t = double(i) - double(FILTER_LEN - 1) / 2.0;
double h = double(i) * (1.0 / double(FILTER_LEN - 1));
double x = (2.0 * f2 * sinc(2.0 * f2 * t) - 2.0 * f1 * sinc(2.0 * f1 * t)) * hamming(h);
m_iFilter[i] = x;
/*
* The actual filter code assumes the impulse response
* is in time reversed order. This will be anti-
* symmetric so the minus sign handles that for us.
*/
x = (2.0 * f2 * cosc(2.0 * f2 * t) - 2.0 * f1 * cosc(2.0 * f1 * t)) * hamming(h);
m_qFilter[i] = -x;
}
}
CHilbert::~CHilbert()
{
delete[] m_iFilter;
delete[] m_qFilter;
delete[] m_iBuffer;
delete[] m_qBuffer;
}
void CHilbert::transform(complex<double>* input, complex<double>* output, int length)
{
wxASSERT(input != NULL);
wxASSERT(output != NULL);
wxASSERT(length > 0);
for (int i = 0; i < length; i++) {
m_iBuffer[m_ptr] = input[i].real();
m_qBuffer[m_ptr] = input[i].imag();
double real = mac(m_iBuffer, m_ptr - FILTER_LEN, m_iFilter, 0);
double imag = mac(m_qBuffer, m_ptr - FILTER_LEN, m_qFilter, 0);
m_ptr++;
if (m_ptr == BUFFER_LEN) {
int ptr = BUFFER_LEN - FILTER_LEN;
for (int j = 0; j < FILTER_LEN; j++) {
m_iBuffer[j] = m_iBuffer[j + ptr];
m_qBuffer[j] = m_qBuffer[j + ptr];
}
m_ptr = FILTER_LEN;
}
output[i] = complex<double>(real, imag);
}
}
void CHilbert::transform(double* input, complex<double>* output, int length)
{
wxASSERT(input != NULL);
wxASSERT(output != NULL);
wxASSERT(length > 0);
for (int i = 0; i < length; i++) {
m_iBuffer[m_ptr] = input[i];
m_qBuffer[m_ptr] = input[i];
double real = mac(m_iBuffer, m_ptr - FILTER_LEN, m_iFilter, 0);
double imag = mac(m_qBuffer, m_ptr - FILTER_LEN, m_qFilter, 0);
m_ptr++;
if (m_ptr == BUFFER_LEN) {
int ptr = BUFFER_LEN - FILTER_LEN;
for (int j = 0; j < FILTER_LEN; j++) {
m_iBuffer[j] = m_iBuffer[j + ptr];
m_qBuffer[j] = m_qBuffer[j + ptr];
}
m_ptr = FILTER_LEN;
}
output[i] = complex<double>(real, imag);
}
}
double CHilbert::sinc(double x) const
{
if (::fabs(x) < 1e-10)
return 1.0;
else
return ::sin(M_PI * x) / (M_PI * x);
}
double CHilbert::cosc(double x) const
{
if (::fabs(x) < 1e-10)
return 0.0;
else
return (1.0 - ::cos(M_PI * x)) / (M_PI * x);
}
double CHilbert::hamming(double x) const
{
return 0.54 - 0.46 * ::cos(2 * M_PI * x);
}
double CHilbert::mac(double* a, int n1, double* b, int n2) const
{
wxASSERT(a != NULL);
wxASSERT(b != NULL);
double sum = 0.0;
for (int i = 0; i < FILTER_LEN; i++)
sum += a[i + n1] * b[i + n2];
return sum;
}
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