at the moment we are busy designing a wide band application using AD9102 produducing a permananet sine wave. With the help of some forum post device now is running.
Setup is fine and frequency and amplitude can easily be adjusted. Requierement is to build a adjustable Sine wave which frequency can be trimed from 4kHz up to 35MHz.
Bassically this works but when I look at the output waveform I am little bit confused concerning output signal quality. Although LVDS is running with 180MHz output of the DDS does not really look like a good sine. Even when a 11,25 MHz sine wave is configuredn it you can easily see quite big resulotion steps. Steps can also be recognized very clear when frequency is set to 1,8 MHz although step size is smaller.
But we need a more smoother output signal where the single steps are not that clear to see.
We thought when using AD9102 with integrated DDS option that there are some signal filter elements are integrated to make a good output signal without having the need to filter externally. This is what we normaly expect when using a DDS and other DDS behave like this.
Of course I can use an external filter for smoothing but before I do this my question:
Is there anything else we have to take into consideration when configuring the device? Is there any chance to influence output quality of the signal or to advice DDS core to make smaller and more steps?
Thanks in advance