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Re: [Discuss-gnuradio] Help : Is this right that the daughterboard passe

From: ton ph
Subject: Re: [Discuss-gnuradio] Help : Is this right that the daughterboard passes data to the usrp board in the I and Q format.
Date: Mon, 25 Apr 2011 19:03:45 +0530

Thanks marcus ,
 i very much appreciate the info and has cleared many of my wrong concepts about usrp and gnuradio. As you have said , processing 100Mhz of bandwidth using gnuradio will be a bit Hard unless handcrafting the signal processing block by hand , what if I processes the 100Mhz bandwidth by a 200Mhz , 12 bit ADC and later on i choose only 10 channels out of my 100Mhz full band data , by a 32 channel DDC , in which i can access each channel data from software.  Which might reduce my bandwidth entering the CPU to about for example: 350 * 10 = 3500 Khz . If i follow this trend, i could reduce much of the overhead to the CPU. But my doubt still exist, processing the 100Mhz bandwidth using gnuradio wil be possible or not ? ... Do we need high IF upto how much so as it can process 100Mhz ... ?

Thanks in advance for your genuine and helpful guide , and again i highly apologize any illogical post from my side .

On Mon, Apr 25, 2011 at 6:35 PM, Marcus D. Leech <address@hidden> wrote:
On 25/04/2011 8:34 AM, ton ph wrote:
Hi marcus
     thanks for immediate reply and your guide was  very helpful from my side ... Now the question is  ,
 suppose,  i have 12 bit  200 mhz adc , and i do not want to reduce my processing bit , as per the instruction from your side it could be
hard to process in my i5 , 4Gb ddr3 configuration computer and also i am not aware  of the IF bandwidth which might require to make
the bandwidth  process instantly ( simultaneously ) . Will gnuradio be able to support the instantaneous processing of the 100Mhz bandwidth,
I have a bit doubt as i learnt that gnuradio can support 8Mhz only.

Thanks , and i highly apologize if my post is a bit out of track or may be called a bit illogical ....

Thanks marcus.

I process 25MHz bandwidth from a USRP2 with my Radio Astronomy applications, on a 6-core AMD Phenom II X6 running at 3.2GHz.

The "8MHz" figure you quote is likely from the original USRP--nothing to do with Gnu Radio, per se.  The USRP1 has a maximum
 bandwidth of 8MHz unless you drop down to 8-bit samples.

The computational load of a signal flow-graph is proportional to bandwidth X complexity.

If you want to process 200Msps, with full 12-bit resolution, you'll need to find some other host interface than 1GiGe--you'd likely
 need to go to a 10GiGe interface.

And while Gnu Radio "scales" arbitrarily, there are limits to the degree to which you can optimize a flow-graph for performance.
 The "Lego brick" approach to constructing processing graphs isn't optimal if really-high performance and low-latency are
 important to you.  In order to process 200Msps, you'd likely need to hand-craft your signal processing chain, and carefully
 parallelize it in an optimal way.  No way are you going to be able to do this on a single-processor machine.

Further, as you point out, the post-mixer bandwidth of the USRP-family daughtercards is limited to much less than 50MHz, in order
 for there not to be an aliases when sampled at the 100Msps rate of the ADC on the USRP.

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