Re: Run USRP at alternate clock frequency?


#1

Clark P. wrote:

I finally got my 44MHz oscillator in. Tried to remove the existing
oscillator but I got nowhere with my iron and copper braid. Can anyone
suggest a cheap tool that will allow me to get this surface mount
oscillator up?

Nope. Its tough unless you have a Metcal talon. I would suggest that
you just cut the traces from the 2 pins on the left side and the one on
the right. This will disable the oscillator, but would be very hard to
undo.

If there were a warranty, this would definitely void it :slight_smile:

The USRP Rev 4’s which are shipping now are much easier to run off an
external oscillator, but that won’t help you.

By the way, we also have very good and fast rational resamplers in the
source. Are you sure that wouldn’t help you?

Matt


#2

Clark P. wrote:

I’ll try the heat gun solution first. (Gives me an excuse to buy one.)

Regarding the rational resampler: that is in software, right? I’m trying
to run at 44 MHz so I can do the despreading for 802.11 inside the FPGA.
I think I can do the differential detection in the fpga too so that the
stream to the PC will just be the raw bits.

Yes, it’s in software. I forgot what you were trying to do.

Matt


#3

I’ll try the heat gun solution first. (Gives me an excuse to buy one.)

Regarding the rational resampler: that is in software, right? I’m trying
to
run at 44 MHz so I can do the despreading for 802.11 inside the FPGA. I
think I can do the differential detection in the fpga too so that the
stream
to the PC will just be the raw bits.

I’ve done some matlab simulations with good results using the USRP to
collect off my own wlan. Even without an equalizer I’m getting near
perfect
packet reception.

Technically, if the packet rate is low enough I could do everything in
software IF I put some smarts in the FPGA to only send the IF samples
that
belong to a packet. But net traffic would have to be less than a couple
percent to be sustainable.

-Clark

oscillator but I got nowhere with my iron and copper braid. Can anyone
The USRP Rev 4’s which are shipping now are much easier to run off an
external oscillator, but that won’t help you.

By the way, we also have very good and fast rational resamplers in the
source. Are you sure that wouldn’t help you?

Matt


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