Re: [Discuss-gnuradio] Sampling rate of USRP and data rate through USB

[Eric Blossom]

On Mon, Nov 06, 2006 at 01:40:21PM +0100, Lin Ji wrote:
> Hi,
>  There is one thing that I can not figure out:
>  The ADC on the USRP has a sampling rate at 64Msps, that is, for a data at
> 1Mbps, for every incoming bit there will be 64 samples. Suppose every sample
> is 16bits, the bit rate is 1024Mbps,that is a huge amount of data flow. Now
> if a user want to same these samples to file through USB, even though the
> USB 2.0 interface has a high throughput at 480Mbps, it's not enough. If
> there is a buffer(like a FIFO or something) that is handling the ADC to USB
> tranfer, sooner or later this buffer will get full, how is this situation
> been handled?
>  Thanks.
> /Lin

This diagram is "close to right":

  http://www.pattoncentral.org/gnuradio/diagram/

There's a digital downconverter (DDC) in the FPGA.

[The downconversion stage in the diagram should show a complex
multplier, not two real multipliers.]

Eric