What Is the Maximum Resistivity Considered Acceptable for an RFID Antenna?

“Maximum resistivity” sounds like something I received from girls in high school. Since I had never heard the term before receiving your question, I reached out to Stephen Schwartz, the VP of engineering at RFID Global Solution, a leading RFID systems integrator and solutions provider. Here is his response:

“If you are referring to the ohms rating of the antenna, then there are no standards for this. Rather, it depends on the reader vendor’s recommendations for the best load-matching characteristics between the radio and antenna. Most vendors require a 50 ohm antenna rating.

“You should probably be concerned about other characteristics of an antenna. At RFID Global Solution, we look to seven important categories when selecting the appropriate antenna for a UHF RFID use case: cost, antenna gain and field pattern, polarization, axial ratio for circularly polarized antennas, frequency range and, lastly, ohm rating.

“Each of these must be taken into consideration when trying to select the most appropriate antenna for a given use case and RFID reader. Think of the selection process as akin to selecting the proper type of eyeglasses (bifocals, sunglasses and so on) and eyeglass prescription (near-sighted, far-sighted, etc.) where each reader vendor and use case has different requirements. We start with our customer’s use-case requirements and our library of related reference designs for selecting the most cost-effective antenna available.”