Currently, I do an experiment with multi-chip high-speed DAC AD9739, but when measuring the DAC output signal, I found highr harmonics. Experimental procedure is as follows: using single frequency sine-wave data of DSP output to FPGA, through FPGA the data returns back to the DAC chip AD9739 and use Spectrum Analyzer to measure the output sine wave signals SFDR. In the spectrum of the output signal, single frequency sine signal's harmonic power is larger, resulting in poor SFDR output signal of DAC , the actual wave figure please see attached pictures. Hardware: signal source si clock chip ADCLK914 clock. Output analog front end of DAC is referring to use methods recommended in the manual, differential output signals connenct 90 Ohm resistor to ground respectively, and then through transformer transfering differential signal to single ended signals, AC coupled, and then plus low-pass filter to get a 1GHz output signal.
I do not know how to promote harmonic power to improve SFDR?
Could you pleas help clarify above.