Modeling and Performance Characterization of UHF RFID Portal Applications

UHF RF indentification systems integration into existing processes is a major challenge for trading companies and retailers. The installation of antennas and interrogators and the portal configuration for achieving a required read rate is difficult, and in most cases, sub-optimally implemented. Therefore, it is essential to understand the relationship between achievable read rates and portal setup demands. In this paper, we describe a novel interrogator-to-tag channel model that can be used to determine the required components prior to system installations and tuning processes. Several model parameters are derived from typical portal setups by means of interrogation zone investigations with a custom-made highly sophisticated mobile field strength recorder. Results have shown that the field coverage of the interrogation zone is independent of the antenna height and we have proven that the three-ray LOS-model fits well with real life conditions. The TAG-model parameters mainly depend on the statistical field strength distribution obtained from two independent interrogation zones. Additional measurements will be required in order to find appropriate or even general values for the proposed bimodal field distribution function of the TAG-model for further measurement independent portal characterizations.