Settling Time for BB60C

Hello,

I am capturing I/Q data of varying frequencies via the BB60C API and need to switch center frequency using bbConfigureIQCenter(). My question is, how long does this configuration take?

For the VSG60A, a frequency switch configuration is listed in the manual as taking ~200 μs, however no mention of this is in the BB60C manual. Another thread on here estimates “10s of ms” for this switch, but is there any documentation or empirical tests done to measure this?

Regards,
Wilson

Hi Wilson,

Yes, empirical tests have been done. A recent test showed a typical switch time at ~43ms.

It’s important to realize that it can depend on a few things. The 43ms above was done by repeatedly switching frequencies with no I/Q data acquisition at each frequency, probably the optimal scenario.

The switch time includes things like sending the stop streaming command to the device, flushing all USB transfers, cleaning up the large arrays allocated in the API, reconfiguring the instrument, and starting up the stream at the new frequency. Some of these are more deterministic than others.

The BB60 is rather slow in this regard. Both the SM200/435 and SP145 devices have something called the I/Q sweep list in the API. This allows you to preconfigure up front a list of frequencies and I/Q sample counts to collect, and execute this all at once. This brings switching time to sub-1ms at the cost of having to know in advance the frequencies you want to switch to.

The VSG60 is similar in that to get the full speed of 200us, you need to feed the switch frequencies far in advance to keep the queue saturated. If you don’t, the full switch time is more like 100ms.

You may contact me directly at aj@signalhound.com if you want to discuss any of these options in more depth.

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