AFSquelch Class Reference

#include <afsquelch.h>

Public Member Functions
	AFSquelch ()
virtual	~AFSquelch ()
void	setCoefficients (unsigned int N, unsigned int nbAvg, unsigned int sampleRate, unsigned int samplesAttack, unsigned int samplesDecay, const double *tones)
	center frequency of tones tested More...
void	setThreshold (double _threshold)
bool	analyze (double sample)
bool	evaluate ()
const double *	getToneSet () const
bool	open () const
void	reset ()

Protected Member Functions
void	feedback (double sample)
void	feedForward ()

Private Attributes
unsigned int	m_nbAvg
	number of power samples taken for moving average More...
unsigned int	m_N
unsigned int	m_sampleRate
unsigned int	m_samplesProcessed
unsigned int	m_samplesAvgProcessed
unsigned int	m_maxPowerIndex
unsigned int	m_nTones
unsigned int	m_samplesAttack
unsigned int	m_attackCount
unsigned int	m_samplesDecay
unsigned int	m_decayCount
unsigned int	m_squelchCount
bool	m_isOpen
double	m_threshold
double *	m_k
double *	m_coef
double *	m_toneSet
double *	m_u0
double *	m_u1
double *	m_power
std::vector< MovingAverage< double > >	m_movingAverages

Detailed Description

AFSquelch: AF squelch class based on the Modified Goertzel algorithm.

Definition at line 28 of file afsquelch.h.

Constructor & Destructor Documentation

AFSquelch()

AFSquelch::AFSquelch

(

)

Definition at line 24 of file afsquelch.cpp.

References cos(), m_coef, m_k, m_movingAverages, m_N, m_nbAvg, m_nTones, M_PI, m_power, m_sampleRate, m_toneSet, m_u0, and m_u1.

                     :
            m_nbAvg(128),
            m_N(24),
            m_sampleRate(48000),
            m_samplesProcessed(0),
            m_samplesAvgProcessed(0),
            m_maxPowerIndex(0),
            m_nTones(2),
            m_samplesAttack(0),
            m_attackCount(0),
            m_samplesDecay(0),
            m_decayCount(0),
            m_squelchCount(0),
            m_isOpen(false),
            m_threshold(0.0)
{
    m_k = new double[m_nTones];
    m_coef = new double[m_nTones];
    m_toneSet = new double[m_nTones];
    m_u0 = new double[m_nTones];
    m_u1 = new double[m_nTones];
    m_power = new double[m_nTones];
    m_movingAverages.resize(m_nTones, MovingAverage<double>(m_nbAvg, 0.0f));

    for (unsigned int j = 0; j < m_nTones; ++j)
    {
        m_toneSet[j] = j == 0 ? 1000.0 : 6000.0;
        m_k[j] = ((double)m_N * m_toneSet[j]) / (double) m_sampleRate;
        m_coef[j] = 2.0 * cos((2.0 * M_PI * m_toneSet[j])/(double) m_sampleRate);
        m_u0[j] = 0.0;
        m_u1[j] = 0.0;
        m_power[j] = 0.0;
        m_movingAverages[j].fill(0.0);
    }
}

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~AFSquelch()

AFSquelch::~AFSquelch ( )

virtual

Definition at line 61 of file afsquelch.cpp.

References m_coef, m_k, m_power, m_toneSet, m_u0, and m_u1.

{
    delete[] m_k;
    delete[] m_coef;
    delete[] m_toneSet;
    delete[] m_u0;
    delete[] m_u1;
    delete[] m_power;
}

Member Function Documentation

analyze()

bool AFSquelch::analyze

(

double

sample

)

Definition at line 116 of file afsquelch.cpp.

References feedback(), feedForward(), m_N, m_nbAvg, m_samplesAvgProcessed, and m_samplesProcessed.

Referenced by NFMDemod::processOneSample().

{

    feedback(sample); // Goertzel feedback

    if (m_samplesProcessed < m_N) // completed a block of N
    {
        m_samplesProcessed++;
        return false;
    }
    else
    {
        feedForward(); // calculate the power at each tone
        m_samplesProcessed = 0;

        if (m_samplesAvgProcessed < m_nbAvg)
        {
            m_samplesAvgProcessed++;
            return false;
        }
        else
        {
            return true; // have a result
        }
    }
}

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evaluate()

bool AFSquelch::evaluate

(

)

Definition at line 188 of file afsquelch.cpp.

References m_isOpen, m_movingAverages, m_nTones, m_samplesAttack, m_samplesDecay, m_squelchCount, and m_threshold.

Referenced by feedForward(), and NFMDemod::processOneSample().

{
    double maxPower = 0.0;
    double minPower;
    int minIndex = 0, maxIndex = 0;

    for (unsigned int j = 0; j < m_nTones; ++j)
    {
        if (m_movingAverages[j].sum() > maxPower)
        {
            maxPower = m_movingAverages[j].sum();
            maxIndex = j;
        }
    }

    if (maxPower == 0.0)
    {
        return m_isOpen;
    }

    minPower = maxPower;

    for (unsigned int j = 0; j < m_nTones; ++j)
    {
        if (m_movingAverages[j].sum() < minPower) {
            minPower = m_movingAverages[j].sum();
            minIndex = j;
        }
    }

//    m_isOpen = ((minPower/maxPower < m_threshold) && (minIndex > maxIndex));

    if ((minPower/maxPower < m_threshold) && (minIndex > maxIndex)) // open condition
    {
        if (m_squelchCount < m_samplesAttack + m_samplesDecay)
        {
            m_squelchCount++;
        }
    }
    else
    {
        if (m_squelchCount > m_samplesAttack)
        {
            m_squelchCount--;
        }
        else
        {
            m_squelchCount = 0;
        }
    }

    m_isOpen = (m_squelchCount >= m_samplesAttack) ;

//  if ((minPower/maxPower < m_threshold) && (minIndex > maxIndex)) // open condition
//  {
//      if ((m_samplesAttack > 0) && (m_attackCount < m_samplesAttack))
//      {
//          m_isOpen = false;
//          m_attackCount++;
//      }
//      else
//      {
//          m_isOpen = true;
//          m_decayCount = 0;
//      }
//  }
//  else
//  {
//      if ((m_samplesDecay > 0) && (m_decayCount < m_samplesDecay))
//      {
//          m_isOpen = true;
//          m_decayCount++;
//      }
//      else
//      {
//          m_isOpen = false;
//          m_attackCount = 0;
//      }
//  }

    return m_isOpen;
}

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feedback()

void AFSquelch::feedback ( double  sample )

protected

Definition at line 144 of file afsquelch.cpp.

References m_coef, m_nTones, m_u0, and m_u1.

Referenced by analyze().

{
    double t;

    // feedback for each tone
    for (unsigned int j = 0; j < m_nTones; ++j)
    {
        t = m_u0[j];
        m_u0[j] = in + (m_coef[j] * m_u0[j]) - m_u1[j];
        m_u1[j] = t;
    }
}

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feedForward()

void AFSquelch::feedForward ( )

protected

Definition at line 158 of file afsquelch.cpp.

References evaluate(), m_coef, m_movingAverages, m_nTones, m_power, m_u0, and m_u1.

Referenced by analyze().

{
    for (unsigned int j = 0; j < m_nTones; ++j)
    {
        m_power[j] = (m_u0[j] * m_u0[j]) + (m_u1[j] * m_u1[j]) - (m_coef[j] * m_u0[j] * m_u1[j]);
        m_movingAverages[j].feed(m_power[j]);
        m_u0[j] = 0.0;
        m_u1[j] = 0.0; // reset for next block.
    }

    evaluate();
}

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getToneSet()

const double* AFSquelch::getToneSet ( ) const

inline

Definition at line 52 of file afsquelch.h.

    {
        return m_toneSet;
    }

open()

bool AFSquelch::open ( ) const

inline

Definition at line 57 of file afsquelch.h.

                      {
        return m_isOpen;
    }

reset()

void AFSquelch::reset

(

)

Definition at line 172 of file afsquelch.cpp.

References m_isOpen, m_maxPowerIndex, m_movingAverages, m_nTones, m_power, m_samplesProcessed, m_u0, and m_u1.

Referenced by NFMDemod::applySettings(), and setThreshold().

{
    for (unsigned int j = 0; j < m_nTones; ++j)
    {
        m_u0[j] = 0.0;
        m_u1[j] = 0.0;
        m_power[j] = 0.0;
        m_movingAverages[j].fill(0.0);
    }

    m_samplesProcessed = 0;
    m_maxPowerIndex = 0;
    m_isOpen = false;
}

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setCoefficients()

void AFSquelch::setCoefficients	(	unsigned int	N,
		unsigned int	nbAvg,
		unsigned int	sampleRate,
		unsigned int	samplesAttack,
		unsigned int	samplesDecay,
		const double *	tones
	)

center frequency of tones tested

Parameters

N	the algorithm "block" size
nbAvg	averaging size
sampleRate	input signal sample rate
samplesAttack	number of results before squelch opens
samplesDecay	number of results keeping squelch open

Definition at line 71 of file afsquelch.cpp.

References cos(), m_attackCount, m_coef, m_decayCount, m_isOpen, m_k, m_maxPowerIndex, m_movingAverages, m_N, m_nbAvg, m_nTones, M_PI, m_power, m_sampleRate, m_samplesAttack, m_samplesAvgProcessed, m_samplesDecay, m_samplesProcessed, m_squelchCount, m_threshold, m_toneSet, m_u0, and m_u1.

Referenced by NFMDemod::applyAudioSampleRate(), and NFMDemod::NFMDemod().

{
    m_N = N;                   // save the basic parameters for use during analysis
    m_nbAvg = nbAvg;
    m_sampleRate = sampleRate;
    m_samplesAttack = samplesAttack;
    m_samplesDecay = samplesDecay;
    m_movingAverages.resize(m_nTones, MovingAverage<double>(m_nbAvg, 0.0));
    m_samplesProcessed = 0;
    m_samplesAvgProcessed = 0;
    m_maxPowerIndex = 0;
    m_attackCount = 0;
    m_decayCount = 0;
    m_squelchCount = 0;
    m_isOpen = false;
    m_threshold = 0.0;

    // 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 opposed 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 (unsigned int j = 0; j < m_nTones; ++j)
    {
        m_toneSet[j] = tones[j] < ((double) m_sampleRate) * 0.4 ? tones[j] : ((double) m_sampleRate) * 0.4; // guarantee 80% Nyquist rate
        m_k[j] = ((double)m_N * m_toneSet[j]) / (double)m_sampleRate;
        m_coef[j] = 2.0 * cos((2.0 * M_PI * m_toneSet[j])/(double)m_sampleRate);
        m_u0[j] = 0.0;
        m_u1[j] = 0.0;
        m_power[j] = 0.0;
        m_movingAverages[j].fill(0.0);
    }
}

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setThreshold()

void AFSquelch::setThreshold

(

double

_threshold

)

Definition at line 271 of file afsquelch.cpp.

References m_threshold, and reset().

Referenced by NFMDemod::applySettings().

{
    qDebug("AFSquelch::setThreshold: threshold: %f", threshold);
    m_threshold = threshold;
    reset();
}

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Member Data Documentation

m_attackCount

unsigned int AFSquelch::m_attackCount

private

Definition at line 76 of file afsquelch.h.

Referenced by setCoefficients().

m_coef

double* AFSquelch::m_coef

private

Definition at line 83 of file afsquelch.h.

Referenced by AFSquelch(), feedback(), feedForward(), setCoefficients(), and ~AFSquelch().

m_decayCount

unsigned int AFSquelch::m_decayCount

private

Definition at line 78 of file afsquelch.h.

Referenced by setCoefficients().

m_isOpen

bool AFSquelch::m_isOpen

private

Definition at line 80 of file afsquelch.h.

Referenced by evaluate(), reset(), and setCoefficients().

m_k

double* AFSquelch::m_k

private

Definition at line 82 of file afsquelch.h.

Referenced by AFSquelch(), setCoefficients(), and ~AFSquelch().

m_maxPowerIndex

unsigned int AFSquelch::m_maxPowerIndex

private

Definition at line 73 of file afsquelch.h.

Referenced by reset(), and setCoefficients().

m_movingAverages

std::vector<MovingAverage<double> > AFSquelch::m_movingAverages

private

Definition at line 88 of file afsquelch.h.

Referenced by AFSquelch(), evaluate(), feedForward(), reset(), and setCoefficients().

m_N

unsigned int AFSquelch::m_N

private

Definition at line 69 of file afsquelch.h.

Referenced by AFSquelch(), analyze(), and setCoefficients().

m_nbAvg

unsigned int AFSquelch::m_nbAvg

private

number of power samples taken for moving average

Definition at line 68 of file afsquelch.h.

Referenced by AFSquelch(), analyze(), and setCoefficients().

m_nTones

unsigned int AFSquelch::m_nTones

private

Definition at line 74 of file afsquelch.h.

Referenced by AFSquelch(), evaluate(), feedback(), feedForward(), reset(), and setCoefficients().

m_power

double* AFSquelch::m_power

private

Definition at line 87 of file afsquelch.h.

Referenced by AFSquelch(), feedForward(), reset(), setCoefficients(), and ~AFSquelch().

m_sampleRate

unsigned int AFSquelch::m_sampleRate

private

Definition at line 70 of file afsquelch.h.

Referenced by AFSquelch(), and setCoefficients().

m_samplesAttack

unsigned int AFSquelch::m_samplesAttack

private

Definition at line 75 of file afsquelch.h.

Referenced by evaluate(), and setCoefficients().

m_samplesAvgProcessed

unsigned int AFSquelch::m_samplesAvgProcessed

private

Definition at line 72 of file afsquelch.h.

Referenced by analyze(), and setCoefficients().

m_samplesDecay

unsigned int AFSquelch::m_samplesDecay

private

Definition at line 77 of file afsquelch.h.

Referenced by evaluate(), and setCoefficients().

m_samplesProcessed

unsigned int AFSquelch::m_samplesProcessed

private

Definition at line 71 of file afsquelch.h.

Referenced by analyze(), reset(), and setCoefficients().

m_squelchCount

unsigned int AFSquelch::m_squelchCount

private

Definition at line 79 of file afsquelch.h.

Referenced by evaluate(), and setCoefficients().

m_threshold

double AFSquelch::m_threshold

private

Definition at line 81 of file afsquelch.h.

Referenced by evaluate(), setCoefficients(), and setThreshold().

m_toneSet

double* AFSquelch::m_toneSet

private

Definition at line 84 of file afsquelch.h.

Referenced by AFSquelch(), setCoefficients(), and ~AFSquelch().

m_u0

double* AFSquelch::m_u0

private

Definition at line 85 of file afsquelch.h.

Referenced by AFSquelch(), feedback(), feedForward(), reset(), setCoefficients(), and ~AFSquelch().

m_u1

double* AFSquelch::m_u1

private

Definition at line 86 of file afsquelch.h.

Referenced by AFSquelch(), feedback(), feedForward(), reset(), setCoefficients(), and ~AFSquelch().

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The documentation for this class was generated from the following files:

• sdrbase/dsp/afsquelch.h
• sdrbase/dsp/afsquelch.cpp