QI bought the AD8361 evaluation kit (AD8361ART-EVAL) from Silica Portugal
When I turn it on I get a dc offset of some tens of mV. Can you tell me how to
eliminate this offset?
AThe AD8361 is a wide bandwidth rms to dc converter. The bandwidth extends up to
2.5GHz. The eval board contains no pre-filtering so simply leaving the input
unconnected and measuring the voltage VRMS, the AD8361 will pick up whatever
spurious signals are in your lab and measure their power.
Ensure that you have the board set up for Ground Referenced mode, as per Figure
2 in the datasheet. IREF -> VPOS, SREF-> GND.
It is not meaningful to talk about offset as the output is a function of the
power of the input signal, rather talk in terms of "intercept" and the
intercept varies with the input frequency as per figure in the datasheet.
To measure the intercept, use a set up (similar to TPC 21) with some accurate
sine source with 75ohm source impedance through 75 ohm coaxial line. Vary the
power level, plot the output level and infer the intercept.