sdrangel/sdrbase/dsp/afsquelch.cpp

215 wiersze
4.8 KiB
C++

///////////////////////////////////////////////////////////////////////////////////
// Copyright (C) 2015 Edouard Griffiths, F4EXB. //
// //
// 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 as version 3 of the License, or //
// //
// 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 V3 for more details. //
// //
// You should have received a copy of the GNU General Public License //
// along with this program. If not, see <http://www.gnu.org/licenses/>. //
///////////////////////////////////////////////////////////////////////////////////
#include <cmath>
#include "dsp/afsquelch.h"
AFSquelch::AFSquelch() :
N(0),
sampleRate(0),
samplesProcessed(0),
maxPowerIndex(0),
nTones(2),
samplesAttack(0),
attackCount(0),
samplesDecay(0),
decayCount(0),
isOpen(false),
threshold(0.0)
{
k = new double[nTones];
coef = new double[nTones];
toneSet = new Real[nTones];
u0 = new double[nTones];
u1 = new double[nTones];
power = new double[nTones];
toneSet[0] = 2000.0;
toneSet[1] = 10000.0;
}
AFSquelch::AFSquelch(unsigned int nbTones, const Real *tones) :
N(0),
sampleRate(0),
samplesProcessed(0),
maxPowerIndex(0),
nTones(nbTones),
samplesAttack(0),
attackCount(0),
samplesDecay(0),
decayCount(0),
isOpen(false),
threshold(0.0)
{
k = new double[nTones];
coef = new double[nTones];
toneSet = new Real[nTones];
u0 = new double[nTones];
u1 = new double[nTones];
power = new double[nTones];
for (int j = 0; j < nTones; ++j)
{
toneSet[j] = tones[j];
}
}
AFSquelch::~AFSquelch()
{
delete[] k;
delete[] coef;
delete[] toneSet;
delete[] u0;
delete[] u1;
delete[] power;
}
void AFSquelch::setCoefficients(int _N, int _samplerate, int _samplesAttack, int _samplesDecay )
{
N = _N; // save the basic parameters for use during analysis
sampleRate = _samplerate;
samplesAttack = _samplesAttack;
samplesDecay = _samplesDecay;
// for each of the frequencies (tones) of interest calculate
// k and the associated filter coefficient as per the Goertzel
// algorithm. Note: we are using a real value (as apposed to
// an integer as described in some references. k is retained
// for later display. The tone set is specified in the
// constructor. Notice that the resulting coefficients are
// independent of N.
for (int j = 0; j < nTones; ++j)
{
k[j] = ((double)N * toneSet[j]) / (double)sampleRate;
coef[j] = 2.0 * cos((2.0 * M_PI * toneSet[j])/(double)sampleRate);
}
}
// Analyze an input signal
bool AFSquelch::analyze(Real *sample)
{
feedback(*sample); // Goertzel feedback
samplesProcessed += 1;
if (samplesProcessed == N) // completed a block of N
{
feedForward(); // calculate the power at each tone
samplesProcessed = 0;
return true; // have a result
}
else
{
return false;
}
}
void AFSquelch::feedback(Real in)
{
double t;
// feedback for each tone
for (int j = 0; j < nTones; ++j)
{
t = u0[j];
u0[j] = in + (coef[j] * u0[j]) - u1[j];
u1[j] = t;
}
}
void AFSquelch::feedForward()
{
for (int j = 0; j < nTones; ++j)
{
power[j] = (u0[j] * u0[j]) + (u1[j] * u1[j]) - (coef[j] * u0[j] * u1[j]);
u0[j] = u1[j] = 0.0; // reset for next block.
}
evaluate();
}
void AFSquelch::reset()
{
for (int j = 0; j < nTones; ++j)
{
power[j] = u0[j] = u1[j] = 0.0; // reset
}
samplesProcessed = 0;
maxPowerIndex = 0;
isOpen = false;
}
void AFSquelch::evaluate()
{
double maxPower = 0.0;
double minPower;
int minIndex = 0, maxIndex = 0;
for (int j = 0; j < nTones; ++j)
{
if (power[j] > maxPower) {
maxPower = power[j];
maxIndex = j;
}
}
minPower = maxPower;
for (int j = 0; j < nTones; ++j)
{
if (power[j] < minPower) {
minPower = power[j];
minIndex = j;
}
}
// principle is to open if power is uneven because noise gives even power
bool open = ((maxPower - minPower) > threshold) && (minIndex > maxIndex);
if (open)
{
if (samplesAttack && (attackCount < samplesAttack))
{
attackCount++;
}
else
{
isOpen = true;
decayCount = 0;
}
}
else
{
if (samplesDecay && (decayCount < samplesDecay))
{
decayCount++;
}
else
{
isOpen = false;
attackCount = 0;
}
}
}