Main Content

firtype

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

collapse all in page

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

collapse all

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

collapse all

Input FIR filter with real and linear phase, specified as one of the following filter System objects:

To check if a filter has linear phase, use the islinphase function. To check if a filter has real coefficients, use the isreal function.

Output Arguments

collapse all

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

expand all

See Also

| |