Re: [Discuss-gnuradio] USRP Update

[Matt Ettus]

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