Jim:
Can you give a sample part #, and I'll go look at the data sheet.
The tag in the photo is an NXP NTAG203 chip in a Smartrac Bullseye inlay, about 10 years old. Smartrac never published the exact part number of Ntag203 in inlay X, and doesn't really exist anymore since merging with Avery. Google shows many old hits on both devices.
For a active reader passive tag, don't the tags just rectify the transmitted signal to produce DC to run the internal tag chip?
Sure, which to me argues against transmission line effects within the tag, i.e. behind the secondary winding, being significant to the VNA trace.
I will read up on non-ideal RF transformers and see if anything "sparks" an idea.
Larry
