firtype

Determine type (1-4) of linear phase FIR filter System object

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Syntax

type = firtype(sysobj)

Description

type = firtype(sysobj) determines the type (1 through 4) of the FIR filter System object™

For more input options, see firtype in Signal Processing Toolbox™.

example

Examples

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Open Live Script

Design a Hilbert transformer of order 30 with a transition width of 0.2π rad/sample. Use least-squares minimization to obtain an equiripple linear-phase FIR filter. Plot the zero-phase response in the interval [–π,π).

d = fdesign.hilbert('N,TW',30,0.2);
Hd = design(d,'equiripple',SystemObject=true);
zerophase(Hd,'whole')

Figure contains an axes object. The axes object with title Zero-Phase Response, xlabel Normalized Frequency ( times pi blank rad/sample), ylabel Amplitude contains an object of type line.

The impulse response of this even-order type-3 filter is antisymmetric.

impz(Hd)

Figure contains an axes object. The axes object with title Impulse Response, xlabel n (samples), ylabel Amplitude contains an object of type stem.

ftype = firtype(Hd)
ftype = 
3

Design a minimum-order Hilbert transformer that has a sample rate of 1 kHz. Specify the width of the transition region as 10 Hz and the passband ripple as 1 dB. Display the zero-phase response of the filter.

fs = 1e3;
d = fdesign.hilbert('TW,Ap',10,1,fs);
hd = design(d,'equiripple',SystemObject=true);
zerophase(hd,-fs/2:0.1:fs/2,fs)

Figure contains an axes object. The axes object with title Zero-Phase Response, xlabel Frequency (Hz), ylabel Amplitude contains an object of type line.

Input Arguments

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Output Arguments

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FIR filter type, defined as one of the following:

1 –– Type 1 filter with even order symmetric coefficients.

2 –– Type 2 filter with odd order symmetric coefficients.

3 –– Type 3 filter with even order antisymmetric coefficients.

4 –– Type 4 filter with odd order antisymmetric coefficients.

Version History

Introduced in R2013a

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See Also

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