AD9864_output signal bandwidth

Q

In AD9864 and AD9874's datasheet, it says, the output signal bandwidth is from
6.8kHz to 270kHz. Would you please help explain why 6.8kHz and 270kHz is got.

A

The decimation factor of the digital filter is programmable from 48 to 960 and
the ADC clock rate is specified between 13 to 26 MHz hence giving ragne of 6.8
KHz to 270 KHz. Note, the usable bandwidth is always assumed to be 1/2 the
complex output word rate (due to transition band of digital filters).