I need a DDS chip with at least 2.5dm output power (the more the better!). And i also would like to scale the amplitude either by programming (which I would prefer) or by changing Rset (digital potentiometer or a voltage-output DAC). It is important that the programmed amplitude should be stable over at least 8MHz bandwith and do not drift by changing the frequency within this bandwith.
Can you recommend me a DDS Chip? I was thinking of AD9858.
DDS was designed with a good spectrum signature or good SFDR performance in mind but not so much in terms of amplitude swing. So with regards to amplification, the practical approach is to cascade an amplifier. Analog Devices has a vast selection of variable gain amplifiers, which can be controlled using voltage, for this kind of application. Kindly check this site for the selection. DDS heavily relies on its clock source on the proper operation of its digital subsystem and signal output. As long as the clock source (coming from crystal or a specialized equipment) has a stable frequency (tolerable drift) and properly configured PLL configuration, then the DDS can be expected to have a good clock stability performance.