I have replicated the frequency-doubling example circuit for the AD835 (see figure 24 in datasheet). It does not seem to work. I have attached screenshots of spectrums for both my 10MHz input signal and my output signal. No strong component of 20MHz appears. On the oscilloscope, I do see the proper phase shift between the different inputs, but that shouldn't matter seeing a strong 20MHz signal. I've check all other connections and the agree with the design of figure 24.
Thank you for your help,