Hello Guoan,
If you use the BB_STREAM_IF flag, the data format is 80MS/s 16bit IF samples. This is the raw data format used internally in the API to create the I/Q data. The samples are full scale and un-calibrated. The center frequency you select should be a multiple of 400kHz. In the frequency domain the IF passband will be centered between 0 Hz and the Nyquist frequency (0.5*fs). The timebase error is not accounted for so frequency will not be exact. Decimation and bandwidth do not apply, it is always 27MHz bandwidth and 80MS/s for the BB60C.
The only benefit to this is that in this mode, the CPU load is very low, since almost no processing is performed on the data, it is simply handed off straight from the device.
Regards,
A.J.
