Solving Delta Function Convolution with Sin Wave

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The discussion focuses on solving the convolution of a delta function and a sine wave within a linear time-invariant system. The user expresses confusion over integrating the delta function, specifically the expression involving two delta functions at different points. Clarifications reveal that the convolution of a function with a delta function results in the function being sampled at the delta's location. The key takeaway is that the convolution integral can be simplified using the sampling property of the delta function, leading to a straightforward solution. The final result is the sum of the sine wave evaluated at the points where the delta functions are located.
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hi

I really need your help ...

for linear time invariant system

f(t) =f1(t) (convolution) f2(t)
f(t) = ∫f1(t).f2 ( t-T)
or f(t) = ∫f1(t-T).f2(t)

where f1(t) = delta function = δ(t).δ(t-2)
and f2(t) = sine wave = sin ( ∏t )

how i can solve this ... my problem is : how can i make this integration with impulse ??


thanks in advance
 
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i forget that ... the limits of integration from (0 ) to (2)
 
error 401 said:
hi

I really need your help ...

for linear time invariant system

f(t) =f1(t) (convolution) f2(t)
f(t) = ∫f1(t).f2 ( t-T)
or f(t) = ∫f1(t-T).f2(t)

where f1(t) = delta function = δ(t).δ(t-2)
and f2(t) = sine wave = sin ( ∏t )

how i can solve this ... my problem is : how can i make this integration with impulse ??


thanks in advance

First, you need to get your convolution integral right.
Then, what do you mean by " f1(t) = delta function = δ(t).δ(t-2) "? It's not an equation I can make sense of ...
 
rude man said:
First, you need to get your convolution integral right.
Then, what do you mean by " f1(t) = delta function = δ(t).δ(t-2) "? It's not an equation I can make sense of ...

i mean how can i solve this integral

∫δ(t).δ(t-2)sin(∏t)
 
\delta(t)\delta(t-2) = 0

And the convolution of a function with zero is zero. Your definition of the convolution integral appears incorrect. I suspect you are not giving us all the details, because the problem makes no sense. What was the original problem? (I know there was one since the limits of integration have already simplified from -inf to inf to 0 to 2)

edit:
I'll go ahead and throw out a property that may be helpful, though what you've given us so far doesn't indicate you will use it. The sampling property states

\int\limits_{a}^{b}\delta(x-c)f(x)dx=f(c)

if b > c > a

This property leads to a very simple result when convolving some function f(t) with an impulse d(t - c).
 
Last edited:
the original problem is : convolution between 2 function ( sine wave and delta function ) but when he sketch delta function ..gives two vertical lines ..one of them at x=0 upward and the other at x=2 downward ...

so how can i solve this ?!

and I really appreciate your assistance :)
 
error 401 said:
the original problem is : convolution between 2 function ( sine wave and delta function ) but when he sketch delta function ..gives two vertical lines ..one of them at x=0 upward and the other at x=2 downward ...

so how can i solve this ?!

and I really appreciate your assistance :)

That is just the sum of two Dirac delta functions.

f_1(x) = \delta(x) + \delta(x-2)

Just write out the convolution integral and use the sampling rule.
 
:D

thank you so much ..
 

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