3 Fundamental Frequency Response Measurement Method: DAC with DUC Enabled

The steps discussed work for a DAC that uses real sampling, meaning one that does not use a digital upconverter (DUC) to upconvert the chosen signal from baseband to the chosen frequency. For a device that uses complex mixers in the transmitter chain, such as an AFE from Texas Instruments (TI), there is a step that you must add to the process of taking a passband flatness sweep. This step is to adjust your numerically controlled oscillator (NCO) frequency such that the output frequency of the DAC is at the appropriate frequency to sweep the output across the frequency band of interest. Handle the NCO for the DAC DUC similarly to the description in the previous installment of this series for capturing a bandwidth of the ADC when using an NCO. As an example, see Figure 3-1 and Figure 3-2, which illustrate an example output network for the transmitter channel and the data taken from a TX channel of the AFE with a matching network of 3GHz of bandwidth.