Understanding Interpolated FIR...

Understanding Interpolated FIR FiltersUnderstanding Interpolated FIR Filters
Richard Lyons Besser Associates 201 San Antonio Circle, Bldg B, Suite 115 Mountain View, CA 94040 +1 650 949 3300 E-mail: r.lyons@ieee.org

1. INTRODUCTION
This article describes a class of digital filters, called interpolated FIR filters, that can implement narrowband lowpass finite impulse response (FIR) filter designs with a significantly reduced computational workload relative to traditional FIR filters. First we'll cover the theory of interpolated FIR filters and then present a design example showing the computational savings results. Interpolated FIR (IFIR) filters are based upon the behavior of an N-tap nonrecursive linear-phase FIR filter when each of its unit delays are replaced with Lunit delays, with the expansion factor L being an integer,