UHF RFID Handset Antenna Design With Slant Polarization for IoT and Future 5G Enabled Smart Cities Applications Using CM Analysis

Radio frequency identification (RFID) is a pivotal technology to realize the Internet of Things (IoT) dreams and considered as a last-mile solution. Therefore, this paper presents a novel compact antenna design for UHF RFID handset with angle-adjustable linear polarization using characteristic mode analysis. The proposed antenna design consists of a multi-orientation dipole partially printed on three sides of C shaped F4B substrate and an internal ground behind the handset screen. First of all, different characteristic modes of multi-orientation dipole and ground plane are analyzed using characteristic mode analysis, which shows that the vertical polarization is provided by ground plane, and the horizontal polarization is produced by the dipole. Secondly, the proposed multi-orientation dipole is connected with internal ground using two metal shorting strips to adjust the polarization angle. Finally, a suitable feeding position is selected to excite the required characteristic modes to get the radiation pattern with slant polarization. This antenna covers whole US UHF RFID band ranging from 902 - 928 MHz. The advantage behind slant polarization lies in reading of RFID tags with both horizontal and vertical orientations. A prototype of antenna with 45-degree linear polarization angle is fabricated to prove the concept, and the measurement results are matched well with simulated results. Furthermore, this paper paves the way to use typical android phone-sized handheld reader as terminal device for future IoT applications ranging from consumer terminal devices to infotainment solutions by providing capability of reading RFID tag with different orientations.