On 18/01/2024 03:25, je.amg...@gmail.com wrote:
Hi,
The R&S generator and the USRP device are synchronized through a 10
MHz reference signal. The transmitter (Tx) emits a pure sine wave at
the carrier frequency F0 + 10KHz. The receiver (Rx) in GNURadio
operates at F0 and is externally synchronized to the 10 MHz reference
out of the R&S generator.
In this configuration, the Master Clock Rate (MCR) is set to 184.32
MHz, and the sampling rate is 15.36 MHz. To ensure stability in the
GNURadio flowgraph, a timesink of 15360 points is utilized to achieve
an integer number of periods. When synchronization is maintained, the
graph remains stable; otherwise, it exhibits sliding behavior.
It is noteworthy that the signal remains stable with the N2900 (B200)
device, regardless of the carrier frequency.
The provided GNURadio flowgraph and accompanying GIF illustrate the
graph's sliding behavior when synchronization is compromised. These
materials are included in the attached documentation.
My guess is that what you're dealing with is differences in synthesizer
architecture on the UBX and WBX and your source.
On the USRP end, when you're on a frequency that isn't an exact multiple
of the reference frequency (32 or 64MHz) used by
the synthesizer, some combination of fractional-N synthesis, and DDC
signal rotation in the FPGA will bring the signal very
close to the desired frequency -- a fraction of a Hz, typically.
When you are tuned to a frequency that is an exact multiple,
the synthesizer doesn't have to use fractional-N synthesis and the
DDC in the FPGA doesn't have to do any rotation.
Because each type of RF synthesizer has slightly different behavior, one
can expect small frequency offsets between
different synthesizers, even when using a common reference. That's my
understanding.
The other issue is that I'm not sure the time sink in Gnu Radio is a
really useful tool for doing what you want to do. But that's
a question for the discuss-gnuradio mailing list, not this one.
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