(1) the performance of AD9957 operating at 200Mhz is significantly lower than that of AD9957 operating at 30Mhz, whether it is related to crystal vibration accuracy or other reasons.
(2) whether ADI has analog up-conversion development board, namely mixer + original source. The output frequency is 200Mhz.
1.) In terms of phase noise performance it is expected that the part would have less jitter as when compared to operating with higher frequencies. This is shown in the datasheet and illustrated by this figure. The reason for this is that the the rms jitter of a clk is somehow consistent. Given that, at higher frequencies, the period if this cycle decreases. Thus the ratio between Δt (which is somehow fixed) due to jitter and the perio(decreasing at increasing frequency) of the pulse increases. This ratio is closely related to the phase noise performance of the DDS part across frequency.
2.) I'm aware that our DDS evaluation boards do not have built in mixers in them. You can navigate to our product portfolio page in the mixers section and browse our evaluation boards that you can use with your application. These products have evaluation boards where you can use coaxial cables to connecte with an AD9957 evaluation board.