On 08/16/2010 09:22 PM, Ian H. wrote:
Please disregard my last. I must have got something wrong in my
testing. It now compiles, but it seems I need to use txrx_xcvr.bin
instead of txrx.bin with the latest git trunk. Please correct me if
this is wrong (note I have XCVR2450 as my daughterboard).
This is correct. Due to the size of the code, the xcvr was split out to
its own file. Also, you are right about the prescaler.
Nonetheless, I still seem to get a time varying frequency offset
between a transmitted and received BPSK waveform, when using the same
local oscillator of 36 MHz at each end. In fact, about every million
samples, this frequency offset disappears, then comes back getting
larger, then smaller and disappears again about 1 million samples
Is this expected when using a reference different to 10 MHz? When I
have used two USRP2s both locked to a 10 MHz reference, I never saw
No, you should not see that. It sounds like it is not locked, and I
think the reason is loop bandwidth. The original setup is for a 10 MHz
compare frequency, and you are using a 1 MHz compare frequency. This
will mess up the loop dynamics by dividing the loop bandwidth by 10.
The greatest common divisor of 100 MHz and 36 MHz is 4 MHz, so I would
use that for the compare frequency. Then also increase the charge pump
current to the maximum. That should bring you closer to the original