firtype - Type of linear phase FIR filter

Syntax

t = firtype(hd)
t = firtype(hm)

Description

The next sections describe common firtype operation with discrete-time and multirate filters.

Discrete-Time Filters

t = firtype(hd) determines the type (1 through 4) of a discrete-time FIR filter object hd, returning the type number in t. Filter hd must be both real and have linear phase.

Filter types 1 through 4 are defined as follows:

• Type 1 — even order symmetric coefficients

• Type 2 — odd order symmetric coefficients

• Type 3 — even order antisymmetric coefficients

• Type 4 — odd order antisymmetric coefficients

When hd is a cascade or parallel filter and therefore has multiple stages, each stage must be a real FIR filter with linear phase. In this case, t is a cell array containing the filter type of each stage.

Multirate Filters

t = firtype(hm) determines the type (1 through 4) of the multirate filter object hm. The filter must be real and have linear phase.

Filter types 1 through 4 are defined as follows:

• Type 1 — even order symmetric coefficients

• Type 2 — odd order symmetric coefficients

• Type 3 — even order antisymmetric coefficients

• Type 4 — odd order antisymmetric coefficients

When hm has multiple sections, all sections must be real FIR filters with linear phase. In this case, t is a cell array containing the filter type of each section.

Examples

Determine the type of the default interpolator for L=4.

l = 4;
hm = mfilt.firinterp(l);
firtype(hm)
ans =

     1

See Also

islinphase

firpr2chfb

freqrespest

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