Abstract-In this paper, the proposed theoretical path-loss prediction procedure and measured results of radio wave propagation in an orchard environment are presented. The path-loss prediction of wireless sensor network (WSN) in a durian (Durio zibethinus Murray) orchard is chosen to be an example of this study. The threedimensional (3-D) modified uniform geometrical theory of diffraction (UTD) for curved impedance surface and the complex source point (CSP) technique for source modeling are employed for theoretical path-loss prediction in this paper. The orchard scenario is modeled using canonical geometries of UTD, such as a dielectric flat surface and cylindrical structures with an impedance surface to respectively represent ground and trees. Moreover, since the wireless sensor node is attached to the outside peel of a hanging durian fruit, the fruit partially acts as a wireless sensor node. Therefore, to obtain greater accuracy in the source radiation pattern, the Gaussian beam (GB) expansion via the CSP technique is used for source modeling. The path loss prediction from the proposed numerical procedure and the measured results are in good agreement. The proposed numerical procedure to calculate the path loss from actual scenario of the orchard is useful for network planning such as the pre-harvesting WSN system and other orchard scenarios.
In this paper, the magnetic field shaping technique using the magnetic field repeater for high frequency radio frequency identification (HF-RFID) system and nearfield communications (NFC) system is proposed. This technique aims to improve the communication area between HF-RFID or NFC reader and passive tag by changing the magnetic field distribution over the original HF-RFID or NFC reader antenna. The multiple rectangular loop resonators cooperating with low loss air variable capacitors are employed to construct the proposed magnetic field repeater. The proposed magnetic field repeater is installed on top of the original HF reader antenna without any direct connection to the original reader antenna. The HF-RFID reader for laundry application is chosen as an example to prove the concept and verify the performance. We found that the communication area between the tag and off-the-shelf HF-RFID reader is improved. The proposed technique is useful for antenna improvement of off-the-shelf HF-RFID system in many applications such as laundry application, product tacking, etc. where a short range with wide communication area are required.
KeywordsHigh frequency (HF) radio frequency identification (RFID), magnetic field repeater, HF-RFID reader antenna, magnetic resonance technique
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