I now use the DDS chip AD9914. The sweep frequency generated by No-Dwell high Ramp generation is 400MHz~960MHz, whose system clock is 2.4GHz, and the frequency step is 2.8MHz. Step intervals is 50ns.The frequency spectrum of the output signal is shown in the appendix, which shows that the flatness of spectrum is not very good. The difference between beginning point and the end point is nearly 10dB. What are the reasons for this problem?
In addition, how to control the amplitude of the output signal under No-Dwell high Ramp generation? Please help me as soon as possible. Thanks very much!
The following is my register configuration.