Designing Narrowband FIR Filters

When you use conventional techniques to design FIR filters with especially narrow bandwidths, the resulting filter lengths may be long. FIR filters with long filter lengths often require lengthy design and implementation times, and are more susceptible to numerical inaccuracy. In some cases, conventional filter design techniques, such as the Parks-McClellan algorithm, may fail the design altogether.

You can use an efficient algorithm, called the Interpolated Finite Impulse Response (IFIR) filter design technique, to design narrowband FIR filters. Using this technique produces narrowband filters that require far fewer coefficients (and therefore fewer computations) than those filters designed by the direct application of the Parks-McClellan algorithm. LabVIEW also uses this technique to produce wideband, lowpass (cutoff frequency near Nyquist) highpass filters (cutoff frequency near zero). Refer to Multirate Systems and Filter Banks by P.P. Vaidyanathan or the paper on interpolated finite impulse response filters by Neuvo, et al., listed in Signal Processing Related Documentation for more information about IFIR filter design.