UHF RFID chip impedance measurement: Balun necessary?

If I want to measure the impedance of an UHF RFID chip as done in http://www.eurasip.org/Proceedings/E...ensitivity.pdf
can there be a problem with a unbalanced to balanced connection from the coaxial cable to the PCB board on page 4, figure 2?

Because the measurement of dipole antenna need a balun, wouldn't the impedance measurement of symmetric RFID chip also require a balun?

Hello,

No, you don't have to worry. You can directly measure the chip in a non-balanced fixture. It is like measuring the impedance of a component with size <<< lambda. of course, measuring a balanced antenna requires a balun.

You mean even if the tag chip has differential ports or single-ended port(with another GND)?
I can't understand it, would u pls tell me in detail, or the theory, thanks a lot! Because i've been confused by it for so long time.