public void BasicWndZeroPad()
{
// Same Input Signal as Example 1, except everything is a power of two
double amplitude = 1.0; double frequency = 32768;
UInt32 length = 1024; double samplingRate = 131072;
double[] inputSignal = mdsplib.DSP.Generate.ToneSampling(amplitude, frequency, samplingRate, length);
// Apply window to the Input Data & calculate Scale Factor
double[] wCoefs = mdsplib.DSP.Window.Coefficients(mdsplib.DSP.Window.Type.Hamming, length);
double[] wInputData = inputSignal.Multiply(wCoefs);
double wScaleFactor = mdsplib.DSP.Window.ScaleFactor.Signal(wCoefs);
// Instantiate & Initialize a new DFT
FFT fft = new FFT();
fft.Initialize(length, length * 3); // Zero Padding = 1024 * 3
// Call the FFT and get the scaled spectrum back
Complex[] cSpectrum = fft.Direct(wInputData);
// Convert the complex spectrum to note: Magnitude Squared Format
// See text for the reasons to use Mag^2 format.
double[] lmSpectrum = cSpectrum.Magnitude();
// Properly scale the spectrum for the added window
lmSpectrum = lmSpectrum.Multiply(wScaleFactor);
// For plotting on an XY Scatter plot generate the X Axis frequency Span
double[] freqSpan = Util.FFT.FrequencySpan(samplingRate, length);
// At this point a XY Scatter plot can be generated from,
// X axis => freqSpan
// Y axis => lmSpectrum
}
public void PhaseUnwrap()
{
// Generate a Phase Ramp between two signals
double[] resultPhase = new double[600];
double[] unwrapPhase = new double[600];
UInt32 length = 2048;
double[] wCoeff = mdsplib.DSP.Window.Coefficients(mdsplib.DSP.Window.Type.FTHP, length);
// Instantiate & Initialize a new DFT
FFT fft = new FFT();
fft.Initialize(length, 3 * length);
for (Int32 phase = 0; phase < 600; phase++)
{
double[] inputSignalRef = mdsplib.DSP.Generate.ToneCycles(7.0, 128, length, phaseDeg: 45.0);
double[] inputSignalPhase = mdsplib.DSP.Generate.ToneCycles(7.0, 128, length, phaseDeg: phase);
inputSignalRef = inputSignalRef.Multiply(wCoeff);
inputSignalPhase = inputSignalPhase.Multiply(wCoeff);
// Call the DFT and get the scaled spectrum back of a reference and a phase shifted signal.
Complex[] cSpectrumRef = fft.Direct(inputSignalRef);
Complex[] cSpectrumPhase = fft.Direct(inputSignalPhase);
// Magnitude Format - Just as a test point
double[] lmSpectrumTest = cSpectrumRef.Magnitude();
UInt32 peakLocation = mdsplib.DSP.Analyze.FindMaxPosition(lmSpectrumTest);
// Extract the phase of 'peak value' bin
double[] resultArrayRef = cSpectrumRef.PhaseDegrees();
double[] resultArrayPhase = cSpectrumPhase.PhaseDegrees();
resultPhase[phase] = resultArrayPhase[peakLocation] - resultArrayRef[peakLocation];
}
unwrapPhase = mdsplib.DSP.Analyze.UnwrapPhaseDegrees(resultPhase);
}
public void DirectInverse()
{
UInt32 length = 2048;
FFT fft = new FFT();
fft.Initialize(length);
double[] wCoeff = mdsplib.DSP.Window.Coefficients(mdsplib.DSP.Window.Type.Hann, length);
double[] inputSignal = mdsplib.DSP.Generate.ToneSampling(1.0, 4000, 44100, length);
double[] inputSignalRef = inputSignal.Multiply(inputSignal);
Complex[] cSpectrum = fft.Direct(inputSignalRef);
double[] lmSpectrum = cSpectrum.Magnitude();
Complex[] cSpectrumI = fft.Inverse(cSpectrum);
}
