I try generate frequency sweep signal using DDS (AD9959).
As i know, The Amplitude of the output signal spectrum multiplies by the sinc envelope.
But AD9959 haven't inverse sinc. Have you got as solution to flatten amplitude of output signal?
Below is the picture of Frequency Sweep at DAC Output.
My configure is: system clock : 500 Mhz,
Figure 1: Frequency Sweep with frequency: 0 - 200 Mhz
Figure 2: Pulse of Frequency Sweep with frequency from 127.5 - 172.5 Mhz
Figure 3: Spectrum of signal on Figure 2.