SignalUtils.IirFilter Method

Overload List

#	Signature	Description
1	procedure IirFilter(const Src: TCplx; out Dst: TCplx; var IIRState: TIirState);	Filter data with an IIR filter.
2	procedure IirFilter(const Src: TSCplx; out Dst: TSCplx; var IIRState: TIirState);
3	procedure IirFilter(const Data: TVec; const Num: TVec; const Den: TVec; LinearPhase: Boolean);	Filter Data and place the result back in Data.
4	procedure IirFilter(const Src: TVec; const Dst: TVec; var IIRState: TIirState);	Filter data with an IIR filter.
5	procedure IirFilter(const Data: TVec; var IIRState: TIirState; LinearPhase: Boolean);	Filter data with an IIR filter.
6	procedure IirFilter(Src: Double; out Dst: Double; var IIRState: TIirState);	Filter data with an IIR filter.
7	procedure IirFilter(Src: Single; out Dst: Single; var IIRState: TIirState);

Overload 1: procedure IirFilter(const Src: TCplx; out Dst: TCplx; var IIRState: TIirState);

Filter data with an IIR filter.

#	Name	Type
1	Src	TCplx
2	Dst	TCplx
3	IIRState	TIirState

Result: stored in self (calling object)

Remarks:

Filters sample Src and places complex output of the filter in Dst.

Overload 2: procedure IirFilter(const Src: TSCplx; out Dst: TSCplx; var IIRState: TIirState);

#	Name	Type
1	Src	TSCplx
2	Dst	TSCplx
3	IIRState	TIirState

Result: stored in self (calling object)

Overload 3: procedure IirFilter(const Data: TVec; const Num: TVec; const Den: TVec; LinearPhase: Boolean);

Filter Data and place the result back in Data.

#	Name	Type
1	Data	TVec
2	Num	TVec
3	Den	TVec
4	LinearPhase	Boolean

Result: stored in self (calling object)

Remarks:

The Iir filter is defined with a transfer function. Num is numerator and Den is denominator. Set LinearPhase to True to double filter attenuation and ensure no phase distortion and no phase delay (except for the initial transition regions).

Overload 4: procedure IirFilter(const Src: TVec; const Dst: TVec; var IIRState: TIirState);

Filter data with an IIR filter.

#	Name	Type
1	Src	TVec
2	Dst	TVec
3	IIRState	TIirState

Result: stored in self (calling object)

Remarks:

Filter data in Src and place the result in Dst. IirState must be initialized with a call to IirInit.

Note
Use this routine for filtering of streaming data.

Examples

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

procedure TForm42.Button1Click(Sender: TObject);
var b,c,Response,Response1,num,den: Vector;
State: TIirState;
n,i: integer;
begin
    Tone(b,300,6/300,0,1);

    //   Alternative: try gaussian noise
    //    b := RandGauss(300);

    c.Size(b);
    ChebyshevIFilter(6,0.2,[0.6],ftLowpass,false,num,den);
    FillChar(State,SizeOf(State),0);
    IirInit(num,den,State);
    try
        //Alternative 1, IIR streaming
        n := 10;
        for i := 0 to (b.Length div n) - 1 do
    begin
        b.SetSubRange(i*n,n);
        c.SetSubRange(i*n,n);
        IirFilter(b,c,State);
    end;

    //Alternative 2 single block filter (does not require TIirState)
    //                c.Copy(b);
    //                IirFilter(c,num,den,True);

    //Alternative 3 single block
    //                c.Copy(b);
    //                IirFilter(c,State);

    c.SetFullRange;
    b.SetFullRange;
    DrawIt([b,c],['Original signal','Filtered signal']);
    FrequencyResponse(b,nil,Response,8,True,wtHanning);
    FrequencyResponse(c,nil,Response1,8,True,wtHanning);
    DrawIt([Response,Response1],['Orig. signal','Filtered']);
finally
    IirFree(State);
end;
end;

Overload 5: procedure IirFilter(const Data: TVec; var IIRState: TIirState; LinearPhase: Boolean);

Filter data with an IIR filter.

#	Name	Type
1	Data	TVec
2	IIRState	TIirState
3	LinearPhase	Boolean

Result: stored in self (calling object)

Remarks:

Filter Data and place the result back in Data. Use this routine for filtering of non-consecutive blocks of data. Set LinearPhase to True to double filter attenuation and ensure no phase distortion and no phase delay.

Overload 6: procedure IirFilter(Src: Double; out Dst: Double; var IIRState: TIirState);

Filter data with an IIR filter.

#	Name	Type	Description
1	Src	Double	scalar
2	Dst	Double
3	IIRState	TIirState

Result: stored in self (calling object)

Remarks:

Filters sample Src and places real valued output of the filter in Dst.

Overload 7: procedure IirFilter(Src: Single; out Dst: Single; var IIRState: TIirState);

#	Name	Type	Description
1	Src	Single	scalar
2	Dst	Single
3	IIRState	TIirState

Result: stored in self (calling object)