# Problem with results of convolved functions

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##### Member level 2
Convolution...

"if the transmitted radio signal bandwidth > the "bandwidth" of the multipath channel, the received signal will be distorted but the received signal strength will not fade as much over a local area"(rappaport,2002)

i assumed -> radio signal bandwidtgh as the input x(t) --> delta funtion
the channel as the filter h(t)---> rectangular function

When i convolved the two functions together. i found that the output y(t) is not distorted...confused..hhmmm

i used this site..to visualize...the convolution
h**p://www-es.fernuni-hagen.de/JAVA/DisFaltung/convol.html

ok thanks

#### lamom

##### Newbie level 6
Convolution...

i think i will be distorted.

from
x(t) * h(t) ====> X(f).H(f)

using FFT, this call fast convolution, with is the same result.
then H(f) will be sin(x)/x function, which will distort spectrum of X(f) for sure...

Yo!

#### ninhawk

##### Member level 2
Re: Convolution...

hi

...I think that: " the bandwidth of the multipath channel " refers to the 'coherence bandwidth'. it's mean the bandwidth of the channel with 'flat' response.
So, if BW of the signal > BW coherence then it (signal) will be distorted, BUT
in a little spatial area (local area) of a few wavelengths, the fading vary just a little.

regards

##### Member level 2
Re: Convolution...

hi nimhawk...

u said the mutlipath channel is in flat response...does it mean i can visualize as an impulse trains u(nT)

i'm trying to grasp the concept..if u dont mind..

thanks..

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