Hi, everybody.

I'm currently working on a SWR/RF Power meter using two AD8307. I would like to use the same circuit that appears on page 21 (or 22 from the beginning of pdf file) under title "1uW to 1kW 50 Ohm Power Meter". The application note says the circuit uses a 158:1 (or 44 dB) voltage attenuator in order to sample the main 50 Ohm transmission line. However, after a quick inspection and calculation I only can verify the 158:1 attenuation which is only 22 dB and not 44 dB as stated.

Am I missing something or is this a datasheet mistake?

Thanks for the help, guys!

I don't know which application note you are referring to. Would you mind providing a link to it?

If it is a voltage ratio, then you must use 20*log10(voltage ratio); if it were a power ratio, then you would use 10*log10(power ratio). 20*log10(158/1) = 44 dB and 10*log10(158/1) = 22 dB; the latter being incorrect. You would need to square the voltage ratio to get the proper number in dB's (technically, power is V^2/R, but I am assuming the impedances that both voltages are across are the same and thus cancel out). So the calculation would be 10*log10(158^2/1^2) = 44 dB