I need to generate complex IQ waveforms with modulation widths up to, say, 70 MHz. And, I need to do that from about 10 MHz to over 4 GHz. I realize I can use something like the AD9122/ADL5375 to do this, but the AD9122 would be overkill, and the ADL5375 only goes down to 400 MHz center frequency, as I understand it. But, my understanding is that with the AD9122 (or other TxDACs) you can generate a complex, wideband modulated signal at center frequencies up to about 40% of the parts maximum clock frequency. Is this correct? If so, supposedly I could use the AD9122/ADL5375 to generate the signals I need from 400 MHz to over 5 GHz, and use just the AD9122 outputs to generate the waveforms down to 10 MHz. Is this correct? If so, how do you actually generate the driving data for the AD9122 to create, for example, a 60 MHz wide 128QAM signal at 150 MHz center frequency? I assume you just take either the I or the Q output in this case. I assume you could, with a dual channel DAC like the AD9122, get two independent modulated outputs. For example, a 50 MHz wide 64 QAM signal at 200 MHz on one DAC and the 60 MHz wide 128 QAM signal at 150 MHz on the other dac? I assume you could not end up with 4 separate modulated signals with this configuration.
Thanks in advance.
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.