AD8362

Dear  Sir/Madam,

When entering a pure - carrier to AD8362 inputs ( frequency of 2.001MHz power of 10dBm ; or 10dBm frequency 2.0016MHz ) , according to the corresponding relationship between voltage and  power , the result is very accurate , is 10dBm . If using a combiner to combine  two 10dBm frequency( one is  2.001MHz and another is 2.0016MHz) together to the input, measured detector of output voltage only increased 61mV, that corresponds to power input is 11.2dBm, actual should be 13dBm, with Agilent of power meter or other instrument measuring the input power, they both show 3dBm increacement, When the frequency interval more than a 1kHz , the  total measured power can reach 12.3dBm .
When the f requency interval smaller than some value, the total power will decrease.
Could you please help clarify above.
Thanks.
  • Take a look at the signal at the ouptut of the AD8362 on an oscilloscope. I think that you may see some ripple.  Your carrier spacing is 600 Hz (i.e. one carrier is 2.001 MHz and the other carrier is at 2.016). That is a very slowly changing envelope. My guess is that you are not doing enough averaging to get a valid rms computation. So my suggestion would be in increase the cap on pin 9 (CLPF) until the output envelope goes away and you have a dc signal.

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