Hi Jing,
Yes, you have to reconfigure the receiver between I/Q captures, and yes, with the BB60, there will always be a gap when switching frequencies. I would expect the gap to be in the 10’s of milliseconds.
Unfortunately there is not a way to improve this with the BB60. Our SM200/435 has an I/Q sweep list feature, which allows for preconfigured I/Q frequency/capture_len pairs to allow for very fast switching times, (120us switch times). I can provide more information on that if desired.
Andrew