The Simple Feedback Comb Filter

What happens when we multiply the output of a delay line by a gain factor then feed it back to the input?

**Figure 7:** The signal flow diagram of a comb filter.
$\begin{figure}\centerline{\scalebox{1}{% \input{comb2.pstex_t}}}\end{figure}$

The difference equation for this filter is

$\displaystyle y(n) = x(n) + gy(n-M),$

If the input to the filter is an impulse

$\displaystyle x(n)=\{1,0,0,\ldots\}$

the output (impulse response) will be ...

**Figure 8:** Impulse response for filter , where $\tau =M/f_s$ .
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