[SI-LIST] Re: RF board Vs High speed board

Crudely, a digital signal can be meaningful even with an appallingly poor 
signal to noise ratio, an RF signal somewhat less so.
The RF signal can have intelligence across several orders of magnitude in 
amplitude and frequency.
(fortunately a digital signal can still be meaningful even if it looks like a 
giant hedgehog on top of Sydney opera house, even
if it wasn't intended to be so!)


Best Regards
 
David Greig
______________________________
GigaDyne Ltd
http://www.gigadyne.co.uk
______________________________

-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On 
Behalf Of Andrew Burnside
Sent: 24 August 2005 18:05
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: RF board Vs High speed board

Hi Lynne/John
 
RF signals are not necessarily narrowband.
For example, Ultra Wideband Signals (becoming more common these days) have a 
bandwidth of at least 0.25 of the carrier
frequency. 
 
The other case that wideband RF is often seen on boards these days is in Direct 
Digital Downconversion architectures. You might
see in excess of 1GHz going into ADCs, and that's only the IF! In this case the 
wideband IF often contains several signals.
 
Usually some steps have been taken by the implementer of an RF system to limit 
the bandwidth, similar to pre-emphasis and
de-emphasis in a high speed digital system. So usually the RF board will have 
slightly more rounded signals, but these may have
higher rms power than the high speed digital system, especially in a PA 
subsystem.
 
Regards
 
Andrew
 
 
________________________________

From: si-list-bounce@xxxxxxxxxxxxx on behalf of Lynne D. Green
Sent: Wed 24/08/2005 17:27
To: johnnfaq@xxxxxxxxx; si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: RF board Vs High speed board



Hello, John,

RF signals are "narrow band", i.e. modulation is superimposed on a carrier 
frequency.  The modulation bandwidth is significantly
smaller than the carrier frequency (your car radio is a good example - carrier 
is around 100kHz, bandwidth is around 20kHz.)  RF
requires filtering to remove the carrier and recover the signal.

High-speed signals are "wide band", i.e. they have significant frequency 
content from DC to hundreds of times the modulation
rate.  For an ideal interconnect, filtering is not required to recover the 
original signal.
(And, although rates are usually given in MHz, they really mean Mbaud.) 

Best regards,
Lynne


"IBIS training when you need it, where you need it."

Dr. Lynne Green
Green Streak Programs
http://www.greenstreakprograms.com
425-788-0412
lgreen22@xxxxxxxxxxxxxx

-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On 
Behalf Of johnn william
Sent: Wednesday, August 24, 2005 4:19 AM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] RF board Vs High speed board

Hi All,

Please anyone in group clarify the difference in handling the RF board compared 
to normal High speed boards.

Thanks in advance.

John


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