Filter Design Toolbox

firhalfband

Design a halfband FIR filter

Syntax

• b = firhalfband(n,fp)
  b = firhalfband(n,win)
  b = firhalfband('minorder',fp,dev)
  b = firhalfband('minorder',fp,dev,'kaiser')
  b = firhalfband(...,'high')
  

Description

b = firhalfband(n,fp) designs a lowpass halfband FIR filter of order N with an equiripple characteristic. N must be selected such that N/2 is an odd integer. fp determines the passband edge frequency, and it must satisfy 0 < fp < 1/2, where 1/2 corresponds to rad/sample.

b = firhalfband(n,win) designs a lowpass Nth-order filter using the truncated, windowed-impulse response method instead of the equiripple method. win is an n+1 length vector. The ideal impulse response is truncated to length n + 1, and then multiplied point-by-point with the window specified in win.

b = firhalfband('minorder',fp,dev) designs a lowpass minimum-order filter, with passband edge fp. The peak ripple is constrained by the scalar dev. This design uses the equiripple method.

b = firhalfband('minorder',fp,dev,'kaiser') designs a lowpass minimum-order filter, with passband edge fp. The peak ripple is constrained by the scalar dev. This design uses the Kaiser window method.

b = firhalfband(...,'high') returns a highpass halfband FIR filter.

Examples

This example designs a minimum order halfband filter with specified maximum ripple:

• b=firhalfband('minorder',.45,0.0001);
  [h,w,s]=freqz(b); s.plot='mag'; s.yunits = 'li';
  fvtool(h,w,s); % Plot magnitude only in linear units
  figure;
  impz(b) % Impulse response is zero for every other sample
  

See Also
firnyquist, gremez

fir1, firls, remez in your Signal Processing Toolbox documentation

References

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.

firceqrip

firlp2lp