Maksym,
The bandwidth parameter controls the FIR filter cutoff frequency on the IQ data stream. The lower limit for IQ bandwidths are below. Additionally, the final IQ bandwidth is reported back to you in the bbQueryStreamInfo function after you initiate an IQ data stream. Ideally, you should target a bandwidth between 20-80% of the sample rate, because with fixed lengths FIR filters, the filter rolloff duration will be constant. If you need a narrower bandwidth, I would suggest either lowering the sample rate, or running an additional larger filter on the IQ data after you acquire it.
case 1,2: return 50.0e3;
case 4: return 50.0e3;
case 8: return 50.0e3;
case 16: return 50.0e3;
case 32: return 50.0e3;
case 64: return 50.0e3;
case 128: return 50.0e3;
case 256: return 20.0e3;
case 512: return 10.0e3;
case 1024: return 5.0e3;
case 2048: return 2.0e3;
case 4096: return 1.0e3;
case 8192: return 0.1e3;
