b = polystab(a)
Use the window method to design a 25th-oder FIR filter with normalized cutoff frequency rad/sample. Verify that it has linear phase but not minimum phase.
h = fir1(25,0.4); h_linphase = islinphase(h) h_minphase = isminphase(h)
h_linphase = 1 h_minphase = 0
Use polystab to convert the linear-phase filter into a minimum-phase filter. Plot the phase responses of the filters.
hmin = polystab(h)*norm(h)/norm(polystab(h)); hmin_linphase = islinphase(hmin) hmin_minphase = isminphase(hmin) hfvt = fvtool(h,1,hmin,1,'Analysis','phase'); legend(hfvt,'h','hmin')
hmin_linphase = 0 hmin_minphase = 1
Verify that the two filters have identical magnitude responses.
hfvt = fvtool(h,1,hmin,1); legend(hfvt,'h','hmin')