Overload List
| # | Signature | Description |
|---|---|---|
| 1 | function BesselFilter(Order: Integer; CutoffFreq: TDoubleArray; FilterType: TFilterType; Analog: Boolean; A: TMtx; B: TVec; C: TVec; out d: Double): Double; | The resulting transfer function is returned in the state-space form with A,B,C,D variables. |
| 2 | function BesselFilter(Order: Integer; CutoffFreq: TDoubleArray; FilterType: TFilterType; Analog: Boolean; Num: TVec; Den: TVec; IirFrequencyTransform: TIirFrequencyTransform): Double; | The resulting transfer function is returned in the numerator/denumerator form with num and den. |
| 3 | function BesselFilter(Order: Integer; CutoffFreq: TDoubleArray; FilterType: TFilterType; Analog: Boolean; z: TVec; p: TVec; var k: Double; IirFrequencyTransform: TIirFrequencyTransform): Double; | Design Bessel IIR filter. |
Overload 1: function BesselFilter(Order: Integer; CutoffFreq: TDoubleArray; FilterType: TFilterType; Analog: Boolean; A: TMtx; B: TVec; C: TVec; out d: Double): Double;
The resulting transfer function is returned in the state-space form with A,B,C,D variables.
| # | Name | Type | Description |
|---|---|---|---|
| 1 | Order | Integer | |
| 2 | CutoffFreq | TDoubleArray | |
| 3 | FilterType | TFilterType | |
| 4 | Analog | Boolean | |
| 5 | A | TMtx | source TMtx |
| 6 | B | TVec | source TVec |
| 7 | C | TVec | source TVec |
| 8 | d | Double |
Returns: Double
Overload 2: function BesselFilter(Order: Integer; CutoffFreq: TDoubleArray; FilterType: TFilterType; Analog: Boolean; Num: TVec; Den: TVec; IirFrequencyTransform: TIirFrequencyTransform): Double;
The resulting transfer function is returned in the numerator/denumerator form with num and den.
| # | Name | Type | Description |
|---|---|---|---|
| 1 | Order | Integer | |
| 2 | CutoffFreq | TDoubleArray | |
| 3 | FilterType | TFilterType | |
| 4 | Analog | Boolean | |
| 5 | Num | TVec | source TVec |
| 6 | Den | TVec | source TVec |
| 7 | IirFrequencyTransform | TIirFrequencyTransform |
Returns: Double
Overload 3: function BesselFilter(Order: Integer; CutoffFreq: TDoubleArray; FilterType: TFilterType; Analog: Boolean; z: TVec; p: TVec; var k: Double; IirFrequencyTransform: TIirFrequencyTransform): Double;
Design Bessel IIR filter.
| # | Name | Type | Description |
|---|---|---|---|
| 1 | Order | Integer | |
| 2 | CutoffFreq | TDoubleArray | |
| 3 | FilterType | TFilterType | |
| 4 | Analog | Boolean | |
| 5 | z | TVec | source TVec |
| 6 | p | TVec | source TVec |
| 7 | k | Double | |
| 8 | IirFrequencyTransform | TIirFrequencyTransform |
Returns: Double
Design Bessel filter of Order with CutoffFreq frequencies and of FilterType type. Set Analog to True, to request an analog filter design in s-plane or set it to false to obtain a digital filter design in z-plane. CutoffFreq must be in range between 0 and 1 (Sampling frequency = 2).
IIrFrequencyTransform specifies when and how will the frequency band transformation be applied. Bessel filters typically do not preserve a flat group delay once transformed to z-domain. The routine uses bilinear transformation to map from s to z-domain. Use matched-Z transform to preserve more phase properties of the Bessel filters in the z-domain. The resulting transfer function is returned in the zero-pole form, with z,p,k variables.
uses MtxExpr, Math387, MtxVec, SignalUtils, MtxVecTee, MtxVecEdit, IirFilters,
LinearSystems;
procedure TForm1.Button1Click(Sender: TObject);
var z,p, num,den, FreqFr,Response: Vector;
Order: integer;
k,Bw,Wc: double;
WcArray: TDoubleArray; //modified 3dB frequency
begin
BesselFilter(5,[3],ftLowpass,True,num,den);
FreqFr.Length := 1000; //Define the frequency grid (logarithmic)
LogRamp(FreqFr,-1,1); //between 0.1 (=10^(-1)) and 10 (=10^1) rad/sec
FrequencyResponseS(num,den,FreqFr,Response); //Laplace
DrawIt(FreqFr,20*Log10(Abs(Response))); //logarithmic frequency and amplitude
end;