firtype() - Signal Processing

t = firtype(b) determines
the type, t, of an FIR filter with coefficients b. t can
be 1, 2, 3, or 4. The filter must be real and have linear phase.examplet = firtype(d) determines
the type, t, of an FIR filter, d. t can
be 1, 2, 3, or 4. The filter must be real and have linear phase.

Syntax

t = firtype(b) examplet = firtype(d) example

Example

Types of Linear Phase FiltersOpen This Example
Design two FIR filters using the window method, one of even order and the other of odd order. Determine their types and plot their impulse responses.
subplot(2,1,1)
b = fir1(8,0.5);
impz(b), title(['Type ' int2str(firtype(b))])

subplot(2,1,2)
b = fir1(9,0.5);
impz(b), title(['Type ' int2str(firtype(b))])

Design two equiripple Hilbert transformers, one of even order and the other of odd order. Determine their types and plot their impulse responses.subplot(2,1,1)
b = firpm(8,[0.2 0.8],[1 1],'hilbert');
impz(b), title(['Type ' int2str(firtype(b))])


subplot(2,1,2)
b = firpm(9,[0.2 0.8],[1 1],'hilbert');
impz(b), title(['Type ' int2str(firtype(b))])

Types of FIR digitalFilter ObjectsOpen This Example
Use designfilt to design the filters from the previous example. Display their types.
d1 = designfilt('lowpassfir','DesignMethod','window', ...
                'FilterOrder',8,'CutoffFrequency',0.5);
disp(['d1 is of type ' int2str(firtype(d1))])
d2 = designfilt('lowpassfir','DesignMethod','window', ...
                'FilterOrder',9,'CutoffFrequency',0.5);
disp(['d2 is of type ' int2str(firtype(d2))])
d3 = designfilt('hilbertfir','DesignMethod','equiripple', ...
                'FilterOrder',8,'TransitionWidth',0.4);
disp(['d3 is of type ' int2str(firtype(d3))])
d4 = designfilt('hilbertfir','DesignMethod','equiripple', ...
                'FilterOrder',9,'TransitionWidth',0.4);
disp(['d4 is of type ' int2str(firtype(d4))])
d1 is of type 1
d2 is of type 2
d3 is of type 3
d4 is of type 4

Output / Return Value

Limitations

Alternatives / See Also

Reference