Single antenna unit with robust near- and far-field for multiband applications

Zusammenfassung

This investigation targets to develop a multi-purpose switched multi-band an- tenna for Radio Frequency IDenti cation (RFID) reader applications. Typically, the RFID systems can be categorized depending on the range of the applications, this de nes a Near-Field (NF) RFID and a Far-Field (FF) RFID, and depending on that the reader and the tag antennas are developed exclusively. Additionally, the RFID systems can be categorized also depending of the frequency of oper- ation, e.g., HF, UHF, 2.46GHz, and 5.8GHz. Therefore, various combinations of the range and frequency categories are possible, but the objective of this re- search is to design a reader antenna which can serve both the NF- and the FF- RFIDs and is able to operate at almost all of the adopted frequencies of the RFID applications in a switching manner. To achieve this goal, the RFID reader antenna is optimized rst for the desired interrogation zone, and then multiple purposes and frequencies are integrated with optimized design. In this regard, a novel Non-uniformly Distributed Turns coil (NDTC) antenna is designed for HF-RFID reader application operating at 13.56MHz. The multiple turns of the NDTC are optimally distributed in inner area of the coil for a signi cantly en- hanced magnetic eld (H- eld) in the NF zone. To include FF interrogation along with the NF, a Segmented-Line NDTC (SL-NDTC) antenna for UHF-RFID reader application is developed and presented as a dual-purpose antenna operating at a single-frequency 915MHz. To integrate the dual-purpose (NF and FF) property with multiple bands of RFID applications, a Dual-Band NDTC (DB-NDTC) an- tenna is proposed operating at switchable frequencies of HF 13.56MHz and UHF 915MHz. The DB-NDTC antenna can interrogate in both NF and FF zones, and when switched to HF persists the robust H- eld of the NDTC antenna in the NF zone, and shows a decent gain and radiation eciency in the FF zone when switched to UHF. Hence, DB-NDTC can be realized as a dual-purpose switch- able dual-band antenna. To achieve the ultimate objective of this research work, a multi-purpose switched multiband antenna is designed using RF-switches and having three modes of operations (mode-1-3) depending of states (ON or OFF) of the switches. In mode-1, 2, and 3, the antenna respectively switches to op- erating frequencies 915MHz, 2.45GHz, and 5.8GHz, where, for each individual mode, it can perform for both NF and FF RFID applications. This demonstrates a switched antenna for multiband behavior designed to be used as multi-purpose RFID reader. During the investigation, analytical and numerical methods are used to develop the designs, and parametric studies using simulator are conducted to optimize the performance of the antennas. The designs are fabricated and the measurement results are corroborated with analytical and simulated results.