Thank you Marcus. So, +-0.01ppb is right.If two USRP x310(both of them use
OCXO) are communicating each other via coaxial cable at the frequency 1GHz, the
receiver usrp x310 have to get the center frequency from (1GHz - 0.02Hz) to
(1GHz + 0.02Hz). I mean, the frequency offset should be within
+-0.02ppb.Because the maximum frequency offset between two USRP X310 would be
-0.02ppb ~ +0.02ppb.Am I right?
-----------------------Original Message-----------------------From: "Marcus D.
Leech via USRP-users" <usrp-users@lists.ettus.com>To:
usrp-users@lists.ettus.comSent date: 2018-05-02 13:54:46 GMT +0900
(ROK)Subject: Re: [USRP-users] X310 frequency accuracy spec
On 05/02/2018 12:32 AM, Hojoon Yang via USRP-users wrote:
Hi, all.
In manual, I see the following sentece.
"The GPSDO improves the accuracy of the internal frequency reference to 20
ppb, or 0.1 ppb if the GPS is synchronized to the GPS constellation."[1]
It said 0.1 ppb if the GPS synchronized. However, in the below table,
Frequency Accuracy is +-0.01ppb.
Question: 0.1 ppb vs 0.01 ppb. what is right?
[1]https://kb.ettus.com/X300/X310
Not sure precisely where those numbers come from.
The Allan Deviation for a typical OCXO-based GPSDO is somewhere in the
ballpark of 1.0e-11, at approximately 1000s integration time.
Whether at any given moment, you're getting 1.0e-10 or 1.0e-11 isn't going
to make much difference for the overwhelming majority
of applications.
Most telecom type applications have built-in frequency-offset compensation
algorithms in the receiver code to cope with offsets well
into the 1PPM or worse, range. Some applications, like TDMA with tight
timing, may require better, which is why external-clocking
options are offered.
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