Determine type (1-4) of linear phase FIR filter System object
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')
The impulse response of this even-order type-3 filter is antisymmetric.
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)
sysobj— Input FIR filter
Input FIR filter with real and linear phase, specified as one of the following filter System objects:
type— FIR filter type
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
4 –– Type 4 filter with odd order antisymmetric