Analysis of Antenna Coupling in Near-Field Communication Systems
Date Issued
2009
Date
2009
Author(s)
Chen, Yen-Sheng
Abstract
Recently, near-field communication systems have been widely used in many applications such as the near-field UHF RFID item-level tagging, the Near Field Communication (NFC) device, and the mCoupons. To successfully design and optimize the near-field communication systems, it is important to investigate the near-field coupling between the transmitting and receiving antennas. In this thesis, a simple formula has been presented for computing the coupling coefficient between two antennas that are placed in the near field of each other. The choices of the two antennas are arbitrary, and all the information needed includes the corresponding normalized vector far-field patterns along with their relative orientations and the antenna spacing. o verify the proposed formulation, the coupling coefficients in several near-field scenarios, including a practical near-field UHF RFID system, are computed and compared to those measured and full-wave simulated using Ansoft HFSS. They are all in good agreement. Additionally, it is shown that several factors may influence the coupling coefficient, such as the impedance matching of the receiving antenna and the directivity of the transmitting antenna. With the aid of the proposed formulation, the near-field read range and read reliability can be determined and the near-field coupling phenomena can be investigated. The results thus obtained may be useful in the near-field communication systems.
Subjects
Electromagnetic coupling
near field
power transmission
RFID
UHF antennas
Type
thesis
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