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Re: [Discuss-gnuradio] USRP2 + WBX How to use a 32 MHz signal band?

From: Vladutzzz
Subject: Re: [Discuss-gnuradio] USRP2 + WBX How to use a 32 MHz signal band?
Date: Wed, 1 Dec 2010 02:49:12 -0800 (PST)

Thank you Marcus, for the very prompt and exhaustive reply!
Mostly it's what I expected, but I am a wee bit worried about the IP
addressing process:
I need to change the IP of one of the USRP2 modules, how do I do that,
considering I use an UDP FPGA image and not UHD?
Also, what IPs should I use in the USPR2 source blocks, now that there's 2
of them?


Marcus D. Leech wrote:
> On 11/30/2010 07:04 PM, Vladutzzz wrote:
>> I am interested in this 2 USRPs approach since I don't have the
>> experience
>> and the knowledge to start messing about inside the FPGA firmware code
>> and
>> have an extra USRP2.
>> How would this go?
>> I tried looking up some info about this topic. I've read some bits and
>> pieces on a few forums. Most of the info is about having one USRP2 module
>> as
>> a transmitter and the other as a receiver.
>> I want them both to be receivers(actually half a receiver) and to
>> complete
>> each other by receiving half of the 32 MHz band (so each would receive 16
>> MHz).
>> How would the USRPs be connected to the same computer? (MIMO cable?)
>> How will the two 16 MHz bands be attached together to form the 32 MHz one
>> (some kind of 2:1 multiplexing - I'm just guessing here)?
>> I am aware of the great load exerted upon the system resources, but I'm
>> trying to make this work anyway.
>> Thanks.
>> Vlad.
> Assuming that you have a big-arsed machine to do this with, here goes:
> Assumptions
>    o phase-coherence between the two isn't an issue (if you're just 
> doing power measurements, it won't be)
>    o you have a very-studly computer
>    o you have two good 1GiGe interfaces
> Start out with two single-usrp sources, address them as appropriate for 
> your two USRP2s.
> 16MHz isn't an available bandwidth out of the USRP2, so use 16.66667MHz, 
> and band-limit it to exactly 16MHz with an FIR bandpass filter.
> Your two USRP2s will each be tuned to a frequency that is 16MHz away 
> from each other.
> Once you have your two band-limited complex signals, detect them, using 
> a complex-to-mag-squared on each of them.
>    Then put the two signals into an adder, and low-pass filter with a 
> single-pole IIR or FIR low-pass filter.  Decimate to taste
>    after filtering.
> -- 
> Marcus Leech
> Principal Investigator
> Shirleys Bay Radio Astronomy Consortium
> http://www.sbrac.org
> _______________________________________________
> Discuss-gnuradio mailing list
> address@hidden
> http://lists.gnu.org/mailman/listinfo/discuss-gnuradio

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