[Prism54-devel] queries

[David Willmore]

On Sat, 2 Oct 2004 10:06:50 -0400, Luis R. Rodriguez
<mcgrof at ruslug.rutgers.edu> wrote:
> On Thu, Sep 30, 2004 at 11:56:59AM -0700, Rafiq Shaikh wrote:
> > If yes,
> > then how is it different than PrismGT?
> 
> I believe it just has cheaper Zero IF:
> 
> http://www.analog.com/Analog_Root/static/productSelection/signalChains/communications/comms_14.html
> http://itpapers.zdnet.com/abstract.aspx?scid=39&sortby=titled&docid=72655
> 
> I'm still not sure exactly what a Zero IF is :)

I don't yet know a lot about 802.11, but I do some about RF, so I can
try to shed some light here.  Normally in a modern radio
receiver/transmitter, they use an architecture called
'superheterodyne' in when the signals take several steps in frequency
between RF and 'baseband'.  Baseband is just the plain modulating
signal--not at RF.  It's sometimes called a 'zero IF'.

IF means Intermediate Frequency.  They're the 'steps' between RF and
baseband.  You could say that the last 'baseband' IF is at 0 Hz, so
could call it a  zero IF.

The practical benefits of a zero IF system (directly converting RF to
baseband) are simplified hardware design and thus lower cost.  The
negetive is poorer filtering of nearby possibly interfering signals. 
As filtering is something that would usually be done at IF--where it's
easier--now it has to be done at RF--where it's harder to do.

Is that at all helpful?

Cheers,
David
N0YMV