public void SpectralAnalysis_NegativeDCOffsetTestWithPhase()
{
const int offset = -100;
var sineGen = new SineWaveGenerator(1000, 100, 52100, offset, Math.PI * 0.34);
var d = sineGen.GetNextXSamples(1042).SelectMany(x => x.Data);
var data = d.ToList();
var fftData = SpectralAnaylser.FFT(data).ToArray();
var dcOffset = SpectralAnaylser.FindDCOffset(fftData);
const double sampleCalculatedOffset = -100.0;
Assert.AreEqual(sampleCalculatedOffset, dcOffset, 0.0001);
}
public void SpectralAnalysis_PositiveDCOffsetTest()
{
const int offset = 100;
var sineGen = new SineWaveGenerator(1000, 100, 52100, offset);
var d = sineGen.GetNextXSamples(1000).SelectMany(x => x.Data);
var data = d.ToList();
var fftData = SpectralAnaylser.FFT(data).ToArray();
var dcOffset = SpectralAnaylser.FindDCOffset(fftData);
const double sampleCalculatedOffset = 100.49514649954881;
Assert.AreEqual(sampleCalculatedOffset, dcOffset, 0.0001);
}
public void SpectralAnalysis_RMSFromPowerSpectrum()
{
var sineGen = new SineWaveGenerator(1000, 100, 52100);
var d = sineGen.GetNextXSamples(1000).SelectMany(x => x.Data);
var data = d.ToList();
var fftData = SpectralAnaylser.FFT(data).ToArray();
var powerSpectrum = SpectralAnaylser.PowerSpectrum(fftData).ToArray();
var expected = Math.Sqrt(data.Select(x => x * x).Sum() / data.Count);
var rmsPowerSpec = SpectralAnaylser.RmsFromPowerSpec(powerSpectrum);
Assert.AreEqual(expected, rmsPowerSpec, 0.0001);
}
public void SpectralAnalysis_PositiveDCOffsetTestWithPhase2()
{
const int offset = 100;
var sineGen1 = new SineWaveGenerator(1000, 20, 52100, offset, Math.PI * 0.34);
var sineGen2 = new SineWaveGenerator(1000, 10, 52100, offset, Math.PI * 0.34);
var d1 = sineGen1.GetNextXSamples(1042).SelectMany(x => x.Data);
var d2 = sineGen2.GetNextXSamples(1042).SelectMany(x => x.Data);
var data = d1.Zip(d2, (i, j) => i + j).ToList();
var fftData = SpectralAnaylser.FFT(data).ToArray();
var dcOffset = SpectralAnaylser.FindDCOffset(fftData);
const double sampleCalculatedOffset = 200.0;
Assert.AreEqual(sampleCalculatedOffset, dcOffset, 0.0001);
}
public void SpectralAnalysis_MultipleDCOffsetTestWithPhase()
{
const int offset1 = 85;
const int offset2 = -50;
var sineGen1 = new SineWaveGenerator(1000, 20, 52100, offset1, Math.PI * 0.34);
var sineGen2 = new SineWaveGenerator(1000, 10, 52100, offset2, Math.PI * 0.71);
var d1 = sineGen1.GetNextXSamples(1000).SelectMany(x => x.Data);
var d2 = sineGen2.GetNextXSamples(1000).SelectMany(x => x.Data);
var data = d1.Zip(d2, (i, j) => i + j).ToList();
var fftData = SpectralAnaylser.FFT(data).ToArray();
var dcOffset = SpectralAnaylser.FindDCOffset(fftData);
const double sampleCalculatedOffset = 35.223304466064626;
Assert.AreEqual(sampleCalculatedOffset, dcOffset, 0.0001);
}
public void SpectralAnalysis_PhaseSpectrum_FromComplexFFT()
{
var sineGen = new SineWaveGenerator(1000, 100, 52100);
var data = sineGen.GetNextXSamples(1000).SelectMany(x => x.Data);
var fftData = SpectralAnaylser.FFT(data).ToArray();
var phaseSpectrum = SpectralAnaylser.PhaseSpectrum(fftData).ToArray();
//First 20 points
var expectedData = new[]
{
0.0,
-0.0817719008353,
-0.162338293035,
-0.240593343449,
-0.31561082457,
-0.386691476229,
-0.453375155817,
-0.515423897005,
-0.572786506438,
-0.625555489858,
-0.673924561297,
-0.718151650664,
-0.758529444166,
-0.795363549908,
-0.828957341093,
-0.859602141888,
-0.887571419288,
-0.913117826042,
-0.93647217888,
-0.957843686925
};
for (var i = 0; i < expectedData.Length; i++)
{
Assert.AreEqual(expectedData[i], phaseSpectrum[i], 0.0001);
}
}
public void SpectralAnalysis_PowerSpectrum_FromComplexFFT()
{
var sineGen = new SineWaveGenerator(1000, 100, 52100);
var data = sineGen.GetNextXSamples(1000).SelectMany(x => x.Data);
var fftData = SpectralAnaylser.FFT(data).ToArray();
var powerSpectrum = SpectralAnaylser.PowerSpectrum(fftData).ToArray();
//First 20 points
var expectedData = new[]
{
0.245170056015,
0.49658325619,
0.515681392978,
0.548785216463,
0.597970475506,
0.66651053222,
0.759341701516,
0.883840416896,
1.05113644411,
1.2783980737,
1.59297851554,
2.04035148994,
2.70034243877,
3.7232172295,
5.41902088726,
8.51292503252,
15.0403276039,
32.666419917,
113.029844515,
4391.24421811
};
for (var i = 0; i < expectedData.Length; i++)
{
Assert.AreEqual(expectedData[i], powerSpectrum[i], 0.0001);
}
}
public void SpectralAnaylserTest_PerformFFT_CorrectlyNormalised()
{
var sineGen = new SineWaveGenerator(1000, 100, 52100);
var data = sineGen.GetNextXSamples(1000).SelectMany(x => x.Data);
var fftData = SpectralAnaylser.FFT(data).ToArray();
//First 20 points
var expectedData = new []
{
new Complex(0.495146499549, 0.0),
new Complex(0.496623688121, -0.0407006202924),
new Complex(0.50110389839, -0.0820705763766),
new Complex(0.508737124447, -0.124816451001),
new Complex(0.519787536456, -0.169723759968),
new Complex(0.534657178111, -0.217708447252),
new Complex(0.553924673868, -0.269885728482),
new Complex(0.578406338433, -0.327667996773),
new Complex(0.60925275643, -0.392911314212),
new Complex(0.648104449026, -0.468144913463),
new Complex(0.697351019157, -0.55694776582),
new Complex(0.760581685582, -0.664598558928),
new Complex(0.843413020917, -0.799265722731),
new Complex(0.955119828191, -0.974348360982),
new Complex(1.11215125365, -1.21351968778),
new Complex(1.34667848596, -1.56298418792),
new Complex(1.73120148717, -2.12675932178),
new Complex(2.47045436902, -3.19844730597),
new Complex(4.45520400945, -6.05525222361),
new Complex(26.9564012368, -38.3272036733)
};
for (var i = 0; i < expectedData.Length; i++)
{
Assert.AreEqual(expectedData[i].Real, fftData[i].Real, 0.0001);
Assert.AreEqual(expectedData[i].Imaginary, fftData[i].Imaginary, 0.001);
}
}
