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SignalUtils.BandFlip Function
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Flip the frequency band.

Pascal
procedure BandFlip(const X: TVec); overload;
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Description

Flip the freqencies of the time domain signal stored in X, so that the DC becomes the Nyquist frequency and the Nyquist frequency becomes the DC. (mirror all frequencies around FS/4) The routine is very fast and can also be used for streaming. X.length must be even.

See Also
Example

The sampling frequency is 256 Hz. A tone has a frequency 6Hz. After flipping the frequencies, the tone has a frequency of: FS/2 - 6 = 122Hz. 

 

  uses MtxExpr, Math387, MtxVec, SignalUtils, MtxVecTee, MtxVecEdit;

  procedure TForm1.Button1Click(Sender: TObject);
  var b,c,Response1, Response2: Vector;
  begin
      b := Sin(Ramp(256, mvDouble, 0,2*Pi*6/256));
      c.Copy(b);
      BandFlip(b);
      DrawIt([c,b],['Original signal','Flipped signal']);
      FrequencyResponse(c,nil,Response1,1,True);
      FrequencyResponse(b,nil,Response2,1,True);
      DrawIt([Response1,Response2],['Spectrum: original signal','Spectrum: flipped signal']);
  end;

 

  #include "MtxExpr.hpp"
  #include "MtxVecEdit.hpp"
  #include "MtxVecTee.hpp"
  #include "SignalUtils.hpp"

  void __fastcall TForm1::BitBtn1Click(TObject *Sender)
  {
      Vector b,c, Response1, Response2;

      b = Sin(Ramp(256, mvDouble, 0,2.0*PI*6/256));
      c.Copy(b);
      BandFlip(b);
      DrawIt(OPENARRAY(TVec*,(c,b)),OPENARRAY(AnsiString,("Original signal","Flipped signal")));
      FrequencyResponse(c,NULL,Response1,1,true);
      FrequencyResponse(b,NULL,Response2,1,true);
      DrawIt(OPENARRAY(TVec*,(Response1,Response2)),OPENARRAY(AnsiString,("Spectrum: original signal","Spectrum: flipped signal")));
  }
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