Summary
International Symposium on Antennas and Propagation
2010
Session Number:3TC2
Session:
Number:3TC2-5
Gain Determination of Small UHF RFID Antenna Structures
Rainer Kronberger, Volker Wienstroer, Barbara Friedmann,
pp.-
Publication Date:2010/11/23
Online ISSN:2188-5079
Summary:
In previous publications it has been shown that the determination of the performance and impedance of RFID tag antennas is far from trivial. In many cases, the evaluation of the antenna is derived from read range measurements. As this is strongly related to the mismatch between the chip and the antenna, information about the true antenna performance itself cannot be given. The difficulty in measuring RFID antennas are related to the fact, that they are very small and that they are mainly designed with symmetrical feeding to the RFID chip. Therefore, a standard coaxial measurement cable cannot be connected without coupling and interferences to the tag antenna. In [1] an advanced method has been proposed which requires an additional battery-powered oscillator as calibrated transmitter on the tag. This allows a quite accurate measurement but always requires the additional transmitting device. In the following, a new method is presented, which is a combination of impedance measurements of the tag antenna and the RFID chip as well as the measurement of the wakeup power of the complete tag which is compared to a reference antenna with RFID chip. In an easy way, this allows the determination of the real gain of the tag antenna with sufficient accuracy.