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High power measurement with external amplifier -hints needed

Question asked by maikhermanns on Nov 16, 2011
Hello Group,

I want to do some high power testing on inductively coupled 13,56MHz RFID Transponders. And I don't want to ruin the Testset ...
There is not much accuracy needed - just a rough feeling of the complex Impedance, but as all the time - I want to know how to do it right.

The goal is to measure the RFID Tags Q (S11) using an untuned coupling loop  and in a second step measuring directly into the transponder chip.
That chip needs a minimum voltage to work in the range of 8 to 12 Volts peak to peak, because it derives its internal microprocessor power from the antennas field..

So I already built a resistive bridge with more than 1W Power handling capability ( similar to the Wiltron 6NF50s)

Now I want to plug in an CATV amplifier module with 30..32dBm Output power to feed the whole thing from the analyzers source.

Unfournatly the needed 6dB splitter for the reference channel would swallow some needed dBs.

So the splitter vs. source match is my problem :

Is there a possibility to use / solder an asymmetric splitter which couples less power to the reference port ?

Has the Amplifiers output impedance a major impact on measurement uncertanity, when followed by the 50R of the Splitter, or is everything before that node compensated ?

Would a high resistance coupling for the reference input work as well (maybe something like 1kOhm - In an older post from Sept. 8, 2009 Dr. Joel suggested an asymmetric Splitter with a 200R and a 50R Resistor in the legs. Would that work.) ?

Or would external Leveling be necessary  or just nice to get that ideal voltage source Node as explained in "Design of an Enhanced Vector Network
Analyzer" from 1997 hp journal ?




BTW: Just for Information -  what maximum CW power can a 85046A testset handle ?, would +30dBm work or kill the couplers ? - and which power can an 85052Calkit handle ?

Kind Regards

Maik  

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