Dear everyone,
I have a misunderstanding with the DAC 34H84. I am using the TSW30SH84 EVM. My setup is configured as follow:
Signal baseband BW Fs = 307.2MHz
DAC 34H84
Interpolation = 4
Sampling Frequency = 1288.8MHz
Complex Mixer NCO Frequency FNCO = 76.8MHz
LO frequency FLO = 1.9232GHz
So, I would like to transmit two bands centered at F1=9.6MHz (Fs/32) and 19.2MHz (Fs/16) at baseband level as depicted on figure 1.
By using the GUI, I am able to cancel the IQ imbalance (QMCxxx variable) and the DC offset (Offsetxxx variable).
Figure 2 shows the measurement of the RF output from the evaluation board.
On the right of the spectrum, you can observe the two bands that I want to transmit centered at FLO+FNCO+F1=2009.6GHz and FLO+FNCO+F2=2019.2MHz.
However, on the left side of the spectrum, you can observe two not desired “images” centered at FLO+FNCO-F1 and FLO+FNCO-F2.
Of course, I didn’t expect this output so do you know where does this images come from? Is it a bad configuration of the DAC or a problem with images coming from interpolation process?
Thanks a lot for the support.
Christophe