Enquiry of impedance response of tag antenna

Hi everybody,

I have a question about impedance response of tag antenna...

{How to define a good impedance response ?}

From the attached 1, the diagram of RHS had a good agreement comparing with that of LHS. Is it because the trendency of both impedance (resistance & reactance) are the same (when resistance is increased, reactance is also increased) in 800MHz - 1GHz? but the LHS diagram, both trendency are opposite, so that the response is bad, is it right?

I had simulated a tag antenna for usage of UHF and get a result of impedance response(attached 2), is the response good or not?

Best Regards,
Guillaume

Hi,
Im not an UHF-RFID specialist, but your jpg1 has a Fresonance at 1.15GHz, your simulation ca at 970MHz_I dont see other differences, then both systems are same quality vs. Freq....
The Meander antenna is for me good, but designed for another Frequency, maybe for 2.4 GHz_these is reason for such "other characteristic"!
K.