Bessel_CascadeCoef
Advanced Analysis Library Only
AnalysisLibErrType Bessel_CascadeCoef (double samplingFrequency, double lowerCutoffFreq, double upperCutoffFreq, IIRFilterPtr filterInformation);
Purpose
 |
Note This function has been superseded by Bessel_CascadeCoefEx. |
Generates the set of cascade form filter coefficients to implement an IIR filter as specified by the Bessel filter model.
filterInformation is the pointer to the filter structure that contains the filter coefficients and the internal filter information. You must allocate this structure by calling AllocIIRFilterPtr before calling this cascade IIR filter design function.
To redesign another filter, first call FreeIIRFilterPtr to free the present filter structure and then call AllocIIRFilterPtr with the new type and order parameters before you call Bessel_CascadeCoef.
If the type and order remain the same, you can call Bessel_CascadeCoef without calling FreeIIRFilterPtr and AllocIIRFilterPtr. In this case, you must properly reset the filtering operation for that structure by calling ResetIIRFilter before the first call to IIRCascadeFiltering.
Example Code
/* Design a cascade lowpass Bessel IIR filter. */
double fs, fl, fh, x[256], y[256];
int type, order;
ssize_t n;
IIRFilterPtr filterInfo;
n = 256;
fs = 1000.0;
fl = 200.0;
order = 5;
type = 0; /* lowpass */
Uniform(n, 17, x);
filterInfo = AllocIIRFilterPtr(type, order);
if(filterInfo!=0) {
Bessel_CascadeCoef(fs, fl, fh, filterInfo);
IIRCascadeFiltering(x, n, filterInfo, y);
FreeIIRFilterPtr(filterInfo);
}
Parameters
| Input | ||
| Name | Type | Description |
| samplingFrequency | double | Specifies the sampling frequency in Hertz. |
| lowerCutoffFreq | double | The lower cutoff frequency of the filter in Hertz. |
| upperCutoffFreq | double | The upper cutoff frequency of the filter in Hertz. |
| filterInformation | IIRFilterPtr | Pointer to the filter structure that contains the filter coefficients and the internal filter information. You must allocate this structure by calling AllocIIRFilterPtr before calling this cascade IIR filter design function. |
Return Value
| Name | Type | Description |
| status | AnalysisLibErrType | A value that specifies the type of error that occurred. Refer to analysis.h for definitions of these constants. |
Additional Information
Library: Advanced Analysis Library
Include file: analysis.h
LabWindows/CVI compatibility: LabWindows/CVI 4.0 and later
Examples
Refer to the following examples that use the Bessel_CascadeCoef function:
- analysis\iirfiltr.cws
Open example - analysis\transmit.cws
Open example