Phase Shift Keying

[kilwan]

So we did some experimental measurements at college involving a carrier sine wave of 2Mhz being modulated using 16PSK and 16QAM modulations.
The information wave was a bunch of randomly generated '1' and '0'.
We observed the modulated signal via oscilloscope and a spectrum analyzer.
This is what we got...

16PSK (

http://imageshack.us/photo/my-images/825/16pskspectrum.jpg)

16QAM (

http://imageshack.us/photo/my-images/404/16qamspectrum.jpg)

Now I get why it's mirror ( cos' of the sums and subs of freq. and what not ... ) and I get the it's centered around 2Mhz (that being the freq. of the carrier wave ) but I don't get why the power (gain or what ever you wonna call it ) is the biggest around that freq. and falls of as we go further away ???

I would really appreciate some insight on that.

 

[IRstuff]

So, you think your generator has infinite power that it can use to make its sidelobes all the same power?

TTFN
faq731-376

 

[kilwan]

No, I'm quite aware that not all sidelobes can be the same power .... that wouldn't even be the same signal in the end I believe.

Ok, I didn't mention that our info. wave (signal ... ) had the freq. of 100KHz (very inconvenient for transmission ergo we modulate it into a carrier wave .... ) But shouldn't our modulated signal be mirrored around 2MHz but have the highest power around 100KHz?

P.S. I would greatly appreciate any book suggestions on that topic

 

[IRstuff]

No, not unless you are doing frequency shifting. Your carrier at 2MHz is essentially always present, therefore, it should have the majority of the energy

TTFN
faq731-376