[USRP-users] B205mini: 0-value Samples When Switching Center Frequency
Marcus D. Leech
mleech at ripnet.com
Fri Oct 27 01:23:18 EDT 2017
On 10/27/2017 12:44 AM, Gilad Beeri (ApolloShield) wrote:
> Thanks Marcus.
> I was told by Ettus in the past that nearby hops (X00's of MHz) should
> take some tens of microseconds to settle (for the AD936x chip), while
> I see 3 milliseconds.
> Can you reconfirm the former saying, or confirm that you also
> experience ~3 milliseconds of 0's when you change frequency with a
> delta of tens of MHz?
> In addition, I would expect that during the settling time, I will get
> garbage data / noise, and not 0 samples. Do you know the reason I get 0's?
My *guess* is that this is the AD9361 doing a "mute during tuning"
thing. I don't know whether that's a feature that can be disabled, and
some point in the code history, it was enabled. A cursory
inspection of the code doesn't reveal anything obvious.
When you experience your zero-valued samples, is it a sharp cutoff, or
is there a ramp into, and out-of the zero-valued-samples state?
Are you using manual or automatic gain control?
> On Thu, Oct 26, 2017 at 5:27 PM Marcus D. Leech via USRP-users
> <usrp-users at lists.ettus.com <mailto:usrp-users at lists.ettus.com>> wrote:
> On 10/26/2017 06:43 AM, Gilad Beeri (ApolloShield) via USRP-users
>> Whenever I switch center frequency with a USRP B205mini (changing
>> to a nearby frequency), I get 3 milliseconds of 0 samples.
>> 1. What's the reason behind that?
>> 2. Can I make some changes that will reduce that timespan
>> without data?
> The analog hardware takes a finite amount of time to switch
> frequencies. During that time, there will inevitably be *some*
> type of glitch.
> A PLL synthesizer will take some amount of time to change
> frequency. Every time you change frequency, you take it out of
> its converged state, and
> it has to re-converge.
> USRP-users mailing list
> USRP-users at lists.ettus.com <mailto:USRP-users at lists.ettus.com>
-------------- next part --------------
An HTML attachment was scrubbed...
More information about the USRP-users