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Using AD9122 to generate a complex modulated signal at, say, 300 MHz center frequency

Question asked by etroy on Apr 14, 2015
Latest reply on Apr 16, 2015 by Biao.H

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.