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Wrong RF output in the range of >250 MHz for AD9959

Question asked by mja on May 24, 2016
Latest reply on May 25, 2016 by mja

Hello AD community!


I am using the AD9959 board. My problem: I can not generate RF signals in the range of >250 MHz. For instance, when I ask to the AD9959 to generate a 300 MHz frequency cosine wave it gives as output a cosine wave of 199 MHz frequency. Another example: if I ask for a 260 MHz frequency cosine wave, the resulting  output is composed of a frequency peak (FFT) at 260MHz of intensity -55 dBm, but it is also present a sideband at 239 MHz of intensity -39 dBm, higher than the actual expected signal!

Thank you so much in advance for any input.


PS: The reference clock for all the above-mentioned examples was set to 500MHz (125 MHz Ref Clk and Multiplier = 4).