public static IEnumerable <Complex> ChirpTransform(Complex[] input, LocalRange range, int sampleRate)
{
var samplesLength = input.Length;
var NM1 = samplesLength + range.ZoomOptions.TargetNumberOfSamples - 1;
var A = Complex.Exp(new Complex(0, -2 * Math.PI * range.LeftThreshold / sampleRate));
var W = Complex.Exp(new Complex(0, -2 * Math.PI * ((range.RightThreshold - range.LeftThreshold) / (2 * (range.ZoomOptions.TargetNumberOfSamples - 1)) / sampleRate)));
var y1 = new Complex[NM1];
var y2 = new Complex[NM1];
for (int k = 0; k < NM1 - 1; k++)
{
if (k < samplesLength)
{
y1[k] = Complex.Pow(A * Complex.Pow(W, k), k) * input[k];
}
else
{
y1[k] = 0;
}
if (k < range.ZoomOptions.TargetNumberOfSamples)
{
y2[k] = Complex.Pow(W, -Math.Pow(k, 2));
}
else
{
y2[k] = Complex.Pow(W, (-Math.Pow((NM1 - k), 2)));
}
}
Convolve(y1, y2);
//that can be improved by move scaling from Convolve to this and process only target number of samples
for (int k = 0; k < range.ZoomOptions.TargetNumberOfSamples; k++)
{
y1[k] *= Complex.Pow(W, Math.Pow(k, 2));
}
return(y1.Take(range.ZoomOptions.TargetNumberOfSamples));
}
public static void AssignZoomedValues(this ObservableDataSource <Point> source, List <double> newValues, LocalRange range)
{
source.SuspendUpdate();
source.Collection.Clear();
var length = newValues.Count;
var skip = (range.RightThreshold - range.LeftThreshold) / range.ZoomOptions.TargetNumberOfSamples;
for (int i = 0; i < length; i += 5)
{
var x = range.LeftThreshold + i * skip;
source.Collection.Add(new Point {
X = x, Y = newValues[i]
});
}
source.ResumeUpdate();
}
private static IEnumerable <Complex> ChirpFFT(float[] data, ChirpModel model, LocalRange range)
{
if (model == null)
{
return(null);
}
var fftComplex = new Complex[data.Length]; // the FFT function requires complex format
for (int i = 0; i < fftComplex.Length; i++)
{
fftComplex[i] = new Complex(data[i], 0.0);// make it complex format (imaginary = 0)
}
return(FFTProcessor.ChirpTransform(fftComplex, range, model.SampleRate));
}
