Clarification on this image

[Girly_girl]

Hi all,

can you please let me know what is this image ( View attachment 1.bmp ) usually refered to as? It is related to OFDM....

What does it represent?

and what are the labels on the axes?

Thanks

 

[keith1200rs]

It would be useful to have some context - where did you find it? It looks a bit like a Bessel function curve, but not quite: Bessel function - Wikipedia, the free encyclopedia

Keith.

 

[Girly_girl]

Hi.. yeap you'r right.
I think it is a spectrum of OFDM..
but im not sure if it is a spectrum of it or is it something else of it if you get what i mean.
I found it from google images when i types ofdm spectrum.. but i m not sure if it is actually a spectrum of an OFDM or did it just come up cuz it is related to it?
Thanks

 

[keith1200rs]

Like this? **broken link removed**

Keith.

---------- Post added at 12:58 ---------- Previous post was at 12:57 ----------

I think this shows a similar image Frequency Modulation Bandwidth, Spectrum & Sidebands :: Radio-Electronics.Com

It is the solution of the Bessel functions which gives rise tot he graphs (and the characteristic shape of them).

Keith.

 

[Girly_girl]

cheers for that.. they are both usefull. thanks

in ur first link, there is a similar image but there is no statement on the axis of the graph.. any idea on that?

 

[keith1200rs]

The x axis is frequency.

Keith.

 

[zorro]

It is a superposition of shifted sinc() functions.
The bold curve (with peak at 6) shows clearly one of the sincs.
It can be:

1) an example of representation in time domain of an ideal binary NRZ unipolar transmission with minimum bandwidth: each sinc is the response a pulse (pulse="1", nopulse="0"). In this case, x-axis is time in units of Tbit.

2) a representation in frequency domain of OFDM. Each curve is a spectrum corresponding to a subcarrier (subcarriers 5 and 7 are not present). In this case, x-axis is frequency in units of 1/Tsymbol.

From the context, it seems it is 2)
Regards

Z