The employment of ultra-high frequency (UHF) from 865 to 965 MHz in Radio Frequency Identification (RFID) application, an automatic identification in the commercial system and company data management, improves the supply chain management and tracking efficiency. Current antenna designs for UHF RFID are either dipoles or patch antennas, which can be printed on various kinds of substrates with different dielectric constants.
This thesis aims to present a new design for the multi-band UHF antenna. The antenna intends to cover four bands, namely all UHF bands in the world for RFID applications. The four bands include the European band (865 ~ 868 MHz), the American band (902 ~ 928 MHz), the Chinese band (940 ~ 943 MHz), and the Japanese band (950 ~ 956 MHz). If antenna resonances are closer to each other, the antenna will become more sensitive. In this case, an increased dimension ground plane can be designed for stabilizing the multi -band antenna. When ground plane is large, the bandwidth becomes narrow as shown in the case for the embedded dual band antenna.
Since the four bands are close to each other in frequency, it is difficult to individually control the antenna resonances. In this thesis, a new novel ground plane configuration was introduced to stabilize the antenna performance. This named stair shaped ground plane not only stabilizes the antenna but also increases the bandwidth.
Figure: 140 mm × 40 mm multi-band antenna with stair shaped ground plane (pink shaded).
Figure: S11 for the final optimized multi-bands antenna simulated using HFSS.