Re: [Discuss-gnuradio] USRP Dimensions & Co-ax Daughter Board

[Eric Blossom]

On Tue, Jun 01, 2004 at 08:07:59PM +0100, Iain Young - G7III wrote:
> Hi All,
> 
> Just found out about the USRP, and was reading the Wiki about it, but
> I couldn't find anything about the dimensions of the actual board.
> 
> Looking at the RF Sections page, I'm guessing the board must be about 115
> by 130mm. Can someone confirm this ? If so, that makes it very close
> to a mini-itx form factor motherboard (And gives me an idea about
> mounting...)

The main board is about 125mm x 135mm.  You'll want to allow room for
oversized daughterboads.  

Matt, can you please post the mechanics specs.  Thanks!

> 
> Also, I noted one of the RF daughter boards will have dual raw co-ax
> connectors. Does that mean (for example) that I could connect two sets
> of downconverters, one to each connector (eg S-Band -> 144MHz -> USRP,
> and K-Band -> S-Band -> 144MHz -> USRP) ?
> 
> If that is the case, can I process signals from both at the same
> time ? Or do I have to select in software which connector I want to 
> use ? Or will the two inputs get mixed, and then I do the processing
> on the combined feed ?

Each Rx daughterboard slot gets two A/D's.  We generally expect that
you'll be using a quadrature down converter, and our current FPGA
configuration makes this assumption in wiring the digital down
converters to the A/D.  This could be changed.

With two Rx daughtercards, you've got 4 A/D's available.  Again, if
you use them with quadrature downconverters, you can simultaneously
use two downconverters, subject to the follow restrictions:
The A/D's must all be running at the same rate, the decimation rate in
the FPGA must be the same.  This shouldn't be a problem.  You do get
independent control of the center freqs of the FPGA based digital
downconverters, and the A/D pairs have separate programmable gain and
offsets.  If you look at the AD9862 data sheet, you'll see all the
knobs that are available for twisting.  The host side provides an
interface to pretty much everything.

The resulting data stream is all muxed together and shoved across the
USB.  You can demux it on the host side.

Eric