Convert FIR Type I lowpass to FIR Type 1 lowpass with inverse bandwidth
g = firlp2lp(b)
g = firlp2lp(b) transforms
the Type I lowpass FIR filter
b with zero-phase
response Hr(w) to a Type I lowpass FIR filter
zero-phase response [1 - Hr(π-w)].
b is a narrowband filter,
be a wideband filter and vice versa. The passband and stopband ripples
g will be equal to the stopband and passband
Overlay the original narrowband lowpass and the resulting wideband lowpass
b = firgr(36,[0 .2 .25 1],[1 1 0 0],[1 5]); zerophase(b); hold on h = firlp2lp(b); zerophase(h);
Saramaki, T, Finite Impulse Response Filter Design, Handbook for Digital Signal Processing. S.K. Mitra and J.F. Kaiser Eds. Wiley-Interscience, N.Y., 1993, Chapter 4.