MODELING AND OPTIMIZATION OF RESONANCE CONDITIONS FOR UHF WIRELESS POWER TRANSMISSION SYSTEMS
DOI:
https://doi.org/10.35546/kntu2078-4481.2025.4.1.34Keywords:
wireless power transmission, UHF RFID, efficiency, optimization, modeling, finite element method, COMSOL MultiphysicsAbstract
This paper presents a numerical simulation of a wireless power transmission system in the ultra-high frequency (UHF) range between two ring loop antennas tuned to a frequency of 868 MHz. This range is widely used in radio frequency identification (RFID) technologies in the European Union and Ukraine, ensuring the availability of hardware and allowing wireless charging of low-power devices to be considered as a possible addition to the standard UHF infrastructure. The antennas are implemented on a printed circuit board and equipped with surface-mount trimming inductors of the SMD 0805 form factor, making them simple in design, inexpensive, and technologically feasible for mass production. The main focus is on the influence of the antenna radius (2.5-6 cm) and the distance between them (1, 2, and 10 cm) on the power transfer coefficient |S21|2, obtained through electrodynamic modeling in the COMSOL Multiphysics software environment. It is shown that at small distances between antennas (1-2 cm), there are optimal radii that ensure maximum energy transfer (up to 60-80%), which is due to the optimal balance of the self- and mutual inductance of the circuits. For larger distances (10 cm), the energy transfer efficiency naturally decreases, but an optimum is also observed at larger radii. The dependence of the optimal LOPT trimming inductance on the antenna radius was additionally studied, allowing us to determine a range of values (40-110 nH) compatible with standard SMD components. The obtained results demonstrate the feasibility of practical optimization of printed circuit antenna parameters for short-range wireless power transmission in the UHF range and confirm the effectiveness of numerical simulation as a design tool for such systems.
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