# Convolution - Signals and Systems

1. Nov 21, 2009

### Air

I will make this my discussion thread. I have many questions to ask which I will post here. Please keep checking. All help will be appreciated.

My first question is: For discrete signal, we use variable 'n' and for continuous signal, we use variable 't'. But is the convolution integral valid for both. E.g. the only difference would be 'n' and 't'. Tau and integral will be the same?

2. Nov 25, 2009

### bhupala

Convolution for a CT signal is defined as
$$y(t) = \int_{-\infty}^{\infty}x(\tau)h(t-\tau)d\tau$$
and for DT it is defined as
$$y[n] = \sum_{k=-\infty}^{\infty}x[k]h[n-k]$$

Thus for DT signal we do not have integral but summation.

Just to distinguish for DT case we call it convolution summation and for CT case we call it integral. But the operation is same!

Bhupala!