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hello my friend you can use max038 its the only ic which will give you 10 and 20Mhz. i am constructing a function generator with that. i bought it from https://www.futurlec.com/cgi-bin/search/search.cgi. or you can use dds technology. i hoped i helped you. (dds offers better sine wave purity).
Another approach, you could build some sort of simple voltage controllable pulse generator that goes from 20-40 MHz, divide it by two with a flip-flop to get a 10-20 MHz square wave, and then feed it through a low-pass filter that passes everything up to 20 MHz and blocks everything above 30 MHz.
In my opinion, for a low cost sine wave oscillator use low cost TCXOs. Some of them produce 10 MHz pulse trains. If it's the case just put a bandpass or lowpass filter after that.
Anyway discrete configurations are also very easy to implement in this freq.
If you can use an NCO instead of a VCO, that's great! A DDS can make a pretty good sinewave.
If your AD9834 circuit is outputting lots of weird harmonics and clock feedthrough, then your LC filter probably needs improvement. It needs to strongly attenuate the clock frequency and above. Be sure to use good RF construction techniques.
A 5th order butterworth should attenuate the clock by over 60dB. If it doesn't, then something is wrong with the filter.
Or maybe the filter is working fine, and it's just a measurement problem such as a long ground lead on the oscilloscope probe.
hey!, 7rots51, did u finally could get a clean output signal from the AD9834BRUZ?, im working with this device, but at 10Mhz the outputsignal it about 200mV without any filter (when should be 600mV), is this happenned to you??