/// <summary>
/// Event handler called when DoWork completes.
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
private void fftWorker_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
if (e.Cancelled)
{
return;
}
FFTData fftData = (FFTData)e.Result;
OnFftReady(new FFTEventArgs(fftData));
}
public FFTEventArgs(FFTData fftData)
{
_scopeData = fftData;
}
/// <summary>
/// Do fft calculations and averaging
/// </summary>
/// <param name="sender">Background worker</param>
/// <param name="e">Arguments</param>
private void fftWorker_DoWork(object sender, DoWorkEventArgs e)
{
try
{
BackgroundWorker worker = sender as BackgroundWorker;
FftWorkerArguments args = (FftWorkerArguments)e.Argument;
lock (PropertyLock)
{
if (_fftSize != args.Samples.Length || _fftAvgWant != args.WantedAverages)
{
if (_fftSize > 0)
{
MemoryPlanCleanUp(); // Plan changed, clean up
}
_fftSize = args.Samples.Length;
_fftAvgWant = args.WantedAverages;
MemoryPlansetup(_fftSize, _fftAvgWant);
_fftAvgCnt = 1; // reset averages
}
if (_windowType != args.WindowType)
{
_windowType = args.WindowType;
_fftAvgCnt = 1; // reset averages
}
}
int s = 0;
for (int i = 0; i < 2 * _fftSize; i = i + 2)
{
_din[i] = args.Samples[s++]; // real part
_din[i + 1] = 0; // imaginary part
}
Windowing(_fftSize, _din, _windowType, 1, _din);
fftw.execute(_fplan);
//convert to dBm
int j = 0;
double scaling = 2 / WindowGain(_fftSize, _windowType);
//scaling for FFT N and window gain; no window WindowGain = N*N
for (int i = 0; i < _fftSize; i++)
{
int avgIndex = _fftAvgCnt % _fftAvgWant;
Complex temp = new Complex(_dout[j], _dout[j + 1]);
_magnitudeSqrt[i, avgIndex] = (temp.Magnitude * temp.Magnitude) * scaling;
//scaling FFT output by N and windowing correction
if (i == 0)
{
_magnitudeSqrt[i, avgIndex] = _magnitudeSqrt[i, avgIndex] / 2;
}
//DC term Scales Differently
if (_magnitudeSqrt[i, avgIndex] <= 5e-14)
{
_magnitudeSqrt[i, avgIndex] = 5e-14; // Clamps to -120 dBm and avoids log10 of 0;
}
_freqDomain[i, avgIndex] = 10 * Math.Log10(_magnitudeSqrt[i, avgIndex] / .05); // Power dBm = 10*log10(volt*volt/impedance/1mW) = 10*log10(volt*volt/50/.001)
_magnitudeSqrt[i, avgIndex] = Math.Sqrt(_magnitudeSqrt[i, avgIndex]);
j += 2;
}
if (_fftAvgCnt >= _fftAvgWant) // Wait until wanted amount collected.
{
double[] fft = new double[_fftSize / 2];
double[] rms = new double[_fftSize / 2];
if (_fftAvgWant > 1)
{
// Calculate average
for (int i = 0; i < fft.Length; i++)
{
double avgTempDb = 0;
double avgTempMagnitude = 0;
for (int f = 0; f < _fftAvgWant; f++)
{
avgTempDb += _freqDomain[i, f]; //sum up FFTAvgWant Spectra to calculate average
avgTempMagnitude += _magnitudeSqrt[i, f];
}
fft[i] = avgTempDb / (_fftAvgWant);
rms[i] = avgTempMagnitude / (_fftAvgWant);
}
}
else
{
for (int i = 0; i < fft.Length; i++)
{
fft[i] = _freqDomain[i, 0];
rms[i] = _magnitudeSqrt[i, 0];
}
}
if (worker == null || worker.CancellationPending)
{
e.Cancel = true;
return;
}
FFTData fftData = new FFTData(fft, rms, args.SamplesPerSecond);
e.Result = fftData;
}
_fftAvgCnt++; //increment pointer to ring buffer for spectra
}
catch (Exception) {}
finally
{
_resetEvent.Set();
}
}
