Hi Ed,
You can use AD9122 + ADL5375 to get 400MHz to 4G output with 70MHz bandwidth. AD9122 output center frequency depends on the configuration of NCO and HB filters. you can find the details in the datasheet. As for the output between 10MHz and 400MHz, you also can use AD9122 to create that. you can send the baseband signal to AD9122 and then configure NCO and HB filters to get the desired the output frequency. Or you can bypass the NCO/HB filters of AD9122 and tuning center frequency in the FPGA then send to AD9122. Either way is ok.
if you want to use AD9122 as two independent DACs, the easiest way is bypass NCO/HB filters and no interpolation. Processing in the FPGA and then send two different data to AD9122.
