AD9739

Dear Sir/Madam,
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 . O utput 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.
Thanks.
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  • I do an experiment with  AD9739a-fmc-ebz-revC eval board and xilinx KC 705 FPGA platform, but when measuring the DAC output signal , I found highr harmonics .Startup initialization is similar to recommended at page 62(Data Sheet AD9737A/AD9739A).I've generated sine wave at 250 MHz and was unpleasantly suprised by the level of harmonics, the actual wave figure please see attached pictures. What could be wrong?

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