Yes, I definitely agree that there’s no way to tell when the tuning is DONE. However, my question was about the ‘shortly after’ part. Should it not be inserted ‘shortly before’, or ‘exactly at’? Since there’s typically no way to look into the future, (yes, of course it is doable), there’s no way for somebody to know that the samples that are before the tag are actually ‘invalid.’
_______________________ Eugene Grayver, Ph.D. Aerospace Corp., Sr. Eng. Spec. Tel: 310.336.1274 ________________________ From: [email protected] [mailto:[email protected]] Sent: Friday, July 14, 2017 12:34 PM To: Eugene Grayver <[email protected]> Cc: [email protected] Subject: Re: [USRP-users] TwinRX tuning timing The frequency tag is inserted at some point shortly after the command-set is issued to the hardware. There's no way for the various bits and pieces to tell when the underlying (mostly analog) hardware has converged to an "acceptable" steady-state operating mode. PLL synthesizers don't instantly switch from one frequency to another, digital (and analog) filters have group delays, etc. The time to achieve steady-state can vary from hardware-type to hardware-type, ambient temperature, size of the frequency step, etc. On 2017-07-14 15:10, Eugene Grayver via USRP-users wrote: I am running some experiments to understand the timing of TwinRX tuning. A very simple experiment shows that the tag indicating a frequency change is not placed at the right sample. Here’s a capture: The dashed line indicates the tag sample number. However, there’s clearly something happening before the tag. Note that I am not using timed commands for this – just a regular tune request. [cid:[email protected]] _______________________ Eugene Grayver, Ph.D. Aerospace Corp., Sr. Eng. Spec. Tel: 310.336.1274 ________________________ _______________________________________________ USRP-users mailing list [email protected]<mailto:[email protected]> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
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