Forum: GNU Radio USRP LO Relocation Latency

Dear gr / USRP fellows,

I'm currently experimenting with USRP B100 Local Oscillator relocation 
time.
I've done some experiments on the RX path by tuning towards and away 
from
an OFDM beacon signal.

I have flushed into the received signal some recognizable "relocation
marks" which allowed me to analyze the
received signal integrity in the temporal vicinity of the relocation
instant.

It looks like the LO responds to the steering command in some 
milliseconds
to about two tens of millisecs,
still "artifacts" such as unsuppressed, dominant carrier or unstable 
gain
remain there for some hundreds of millisecs.

I saw that the wiki states "perhaps a second" as the LO settling time.
But can anybody confirm the above behaviour analysis ?


best regards

vince

On 09/26/2012 01:00 PM, Vincenzo Pellegrini wrote:
>
> It looks like the LO responds to the steering command in some milliseconds
> to about two tens of millisecs,
> still "artifacts" such as unsuppressed, dominant carrier or unstable gain
> remain there for some hundreds of millisecs.
>
> I saw that the wiki states "perhaps a second" as the LO settling time.
> But can anybody confirm the above behaviour analysis ?

It depends on the daughterboard. SBX and WBX have a worst case settling
time of about 300us according to the ADI docs.

You should also be able to schedule tuning through time commands so that
the window of "interruption" is explicitly between time X and X + 300us.

Here is some psudo code involving using timed commands to tune:
http://files.ettus.com/uhd_docs/manual/html/sync.h...


-josh

Hi Josh, thanks for the answer,

so you confirm times in the range of the hundreds of micro secs?
are WBX and SBX the best performing daughterboards in this repsect?

where can I find the ADI docs you quote in your email?

thank you and best regards.


vince

2012/9/26 Josh Blum <josh@ettus.com>

> Hi Josh, thanks for the answer,
>
> so you confirm times in the range of the hundreds of micro secs?
> are WBX and SBX the best performing daughterboards in this repsect?
>
> where can I find the ADI docs you quote in your email?
Both boards use the ADF4350 synthesizer.  Analog devices has datasheets
available on their website.