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Re: [Discuss-gnuradio] USRP Update
From: |
Matt Ettus |
Subject: |
Re: [Discuss-gnuradio] USRP Update |
Date: |
Tue, 06 Dec 2005 13:50:30 -0800 |
User-agent: |
Mozilla Thunderbird 1.0.7-1.1.fc4 (X11/20050929) |
Weber, Michael J. (US SSA) wrote:
> Matt, can you elaborate on the 20MHz bandwidth figure for the Flex400
> and give some USRP application guidance? I have this "8MHz maximum
> supportable bandwidth" figure in my head which I think came from the
> sampling/decimation rates + USB2 throughput limitation discussed in the
> USRP documentation..? Some folks have seen the release below and are
> asking me if we can do XYZ in terms of bandwidth and I'm not sure what
> to say at this point.
>
> Is there a way to move 20MHz-wide signals between the host machine and
> the Flex400?
20 MHz bandwidth indicates the width of the baseband filters. Thus, you
can tune digitally anywhere +/- 10 MHz from the LO. If you use 16 bit
samples, you can't get that much over the USB bus at once.
So why is 20 MHz useful? Here are 3 example scenarios:
- You could simultaneously receive or transmit 2 separate signals which
are 4 MHz wide each, which are separated by 12 MHz.
- You can use 8 bit samples, and get 16 MHz of bandwidth. If you were a
radio astronomer, you could use 4-bit samples and get 32 MHz of bandwidth.
- You could do a wideband mod and demod in the FPGA. You would be able
to deal with much wider signals, and send a lower bit rate over the bus.
Matt