Interpolating FIR filters

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This page offers a brief explanation of interpolation FIR filters.


Assume we start with the sample . Padding with zeros gives: . Let's apply 2 filters.

Filter 1: (also written as ).

This filter gives: . This is a hold function.

Filter 2: (also written as

This filter gives: . This is a linear interpolater.

Multiply/add Operations

I had a lot of trouble finding generic information about the number of multiply/add operations used in an interpolation FIR filter. I did find formula for the number of multiply/add operation used by the MATLAB function upfirdn, which upsamples, applies an FIR filter, and then downsamples. It is: where and are the lengths of (the impulse response of the FIR filter) and (the original signal), respectively.

Related Topics

Check out my article on Decimating FIR filters.


Christopher Garrison Lau I