coeffs

Returns the filter System object coefficients in a structure

Syntax

s = coeffs(sysobj)

s = coeffs(sysobj,'Arithmetic',arithType)

Description

s = coeffs(sysobj) returns the coefficients of filter System object™, sysobj, in the structure s.

s = coeffs(sysobj,'Arithmetic',arithType) returns filter coefficients for the filter System object sysobj with the arithmetic specified in arithType.

Examples

Coefficients of an FIR Halfband Interpolator

FIRHalfbandInterp = dsp.FIRHalfbandInterpolator('Specification',...
    'Filter order and transition width','FilterOrder',26);
C = coeffs(FIRHalfbandInterp);
C.Numerator

ans = 1×27

    0.0525         0   -0.0379         0    0.0537         0   -0.0771         0    0.1172         0   -0.2060         0    0.6345    1.0000    0.6345         0   -0.2060         0    0.1172         0   -0.0771         0    0.0537         0   -0.0379         0    0.0525

% Impulse response of the filter
fvtool(FIRHalfbandInterp,'impulse')

Input Arguments

sysobj — Input filter

filter System object

Input filter, specified as as one of the following filter System objects:

• dsp.AllpassFilter

• dsp.AllpoleFilter

• dsp.BiquadFilter

• dsp.CICCompensationDecimator

• dsp.CICCompensationInterpolator

• dsp.CoupledAllpassFilter

• dsp.Differentiator

• dsp.FilterCascade

• dsp.FIRDecimator

• dsp.FIRFilter

• dsp.FIRHalfbandDecimator

• dsp.FIRHalfbandInterpolator

• dsp.FIRInterpolator

• dsp.FIRRateConverter

• dsp.FourthOrderSectionFilter

• dsp.HighpassFilter

• dsp.IIRFilter

• dsp.IIRHalfbandDecimator

• dsp.IIRHalfbandInterpolator

• dsp.LowpassFilter

• dsp.NotchPeakFilter

• dsp.SOSFilter

• dsp.VariableBandwidthFIRFilter

• dsp.VariableBandwidthIIRFilter

arithType — Arithmetic type

'double' (default) | 'single' | 'Fixed'

Arithmetic used in the filter analysis, specified as 'double', 'single', or 'Fixed'. When the arithmetic input is not specified and the filter System object is unlocked, the analysis tool assumes a double-precision filter. When the arithmetic input is not specified and the System object is locked, the function performs the analysis based on the data type of the locked input.

The 'Fixed' value applies to filter System objects with fixed-point properties only.

When the 'Arithmetic' input argument is specified as 'Fixed' and the filter object has the data type of the coefficients set to 'Same word length as input', the arithmetic analysis depends on whether the System object is unlocked or locked.

• unlocked –– The analysis object function cannot determine the coefficients data type. The function assumes that the coefficients data type is signed, has a 16-bit word length, and is auto scaled. The function performs fixed-point analysis based on this assumption.

• locked –– When the input data type is 'double' or 'single', the analysis object function cannot determine the coefficients data type. The function assumes that the data type of the coefficients is signed, has a 16-bit word length, and is auto scaled. The function performs fixed-point analysis based on this assumption.

To check if the System object is locked or unlocked, use the isLocked function.

When the arithmetic input is specified as 'Fixed' and the filter object has the data type of the coefficients set to a custom numeric type, the object function performs fixed-point analysis based on the custom numeric data type.

Output Arguments

s — Structure

struct

Structure with a single field, Numerator, containing filter coefficients.