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# Why Can Discrete-Time FIR Digital Filters be a Linear Phase?

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Why can discrete-time FIR digital filters be made exactly linear phase, whereas IIR digital filters cannot?

I only require a sentence describing why - not any derivations of formulas etc!!!.

I know what makes a filter exactly linear phase (impulse response must be symmetrical), but i don't know why IIR filters cannot be made linear? Is it to do with their feedback and past outputs???

Please just a statement not any matematical derivations!

##### Solution Summary

Why can discrete-time FIR digital filters be made exactly linear phase, whereas IIR digital filters cannot?

I only require a sentence describing why - not any derivations of formulas etc!!!.

I know what makes a filter exactly linear phase (impulse response must be symmetrical), but i don't know why IIR filters cannot be made linear? Is it to do with their feedback and past outputs???

Please just a statement not any mathematical derivations!

##### Solution Preview

Linear Phase" refers to the condition where the phase response of the filter is a linear (straight-line) function of frequency (excluding phase wraps at +/- 180 degrees). This results in the delay through the filter being the same at all frequencies. Therefore, the filter does not cause "phase distortion" or "delay distortion". The lack of phase/delay ...