Random sampling

GNU Radio
1

Hello All…

I am new to gnuradio and the USRP and I am trying to find a way to send
pseudorandomly selected samples from the ADC down the USB pipe to
gnuradio
for processing. I have an algorithm for selecting the samples, but I am
not
sure as to which parts of the Verilog source files I need to change in
order
to reconfigure the FPGA for my needs.

If anyone can point me in the right direction, I would greatly
appreciate
it.

Thanks a lot…

Dustin

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2

On Thu, Jun 19, 2008 at 12:00 AM, dustin_m [email protected] wrote:

Hello All…

I am new to gnuradio and the USRP and I am trying to find a way to send
pseudorandomly selected samples from the ADC down the USB pipe to gnuradio
for processing. I have an algorithm for selecting the samples, but I am not
sure as to which parts of the Verilog source files I need to change in order
to reconfigure the FPGA for my needs.

Welcome aboard - I’m confused. You just want random samples? Is
there anything stopping you from performing said algorithm at the host
on a randomly decimated sample stream?

May I inquire on your application?

Brian

3

dustin_m wrote:

You’ll need to remove the halfband and CIC decimators and put your block
between the CORDIC (if you need it) and the usb interface.

Matt

4

I am new to gnuradio and the USRP and I am trying to find a way to send
pseudorandomly selected samples from the ADC down the USB pipe to gnuradio
for processing. I have an algorithm for selecting the samples, but I am not
sure as to which parts of the Verilog source files I need to change in order
to reconfigure the FPGA for my needs.

This sounds like a good idea! I would also be interested in this kind
of functionality.

Welcome aboard - I’m confused. You just want random samples? Is
there anything stopping you from performing said algorithm at the host
on a randomly decimated sample stream?

May I inquire on your application?

I guess one application would be wide-band alias-free spectrum
estimation (at least that is what I would do with such a sampler).

http://matwbn.icm.edu.pl/ksiazki/amc/amc15/amc1544.pdf

juha

5

On Thu, Jun 19, 2008 at 7:02 PM, Dustin M. [email protected]
wrote:

Juha, Brian,

I am working on a research project that involves wide-band spectral
estimation with the USRP. In this case, the bottleneck is USB 2.0, which is
why I need to implement my sample selection algorithm on the FPGA.

Interesting. Well, I’d start at the top level:

http://gnuradio.org/trac/browser/gnuradio/trunk/usrp/fpga/toplevel/usrp_std/usrp_std.v

If you need no cordic, CIC or halfband filter, just rip out the entire
RX chain and place your algorithm there. The raw ADC samples are
rx_a_a/b and rx_b_a/b.

Sounds like fun. Good luck!

Brian

6

Juha, Brian,

I am working on a research project that involves wide-band spectral
estimation with the USRP. In this case, the bottleneck is USB 2.0,
which is why I need to implement my sample selection algorithm on the
FPGA.

Thanks for your interest.