A Complete Flow of Miniaturizing Coil Antennas Based on Matching Circuit

Abstract

This paper proposes and verifies a complete design flow of miniaturizing a coil antenna and widening its impedance bandwidth for near-field application, such as NFC, RFID and WPT. The proposed scheme based on mature electronic element matching technology is interpreted in detail by two equivalent circuit models in theory. For convenience, only the series equivalent circuit and its matching circuit are respectively established in the circuit simulator ADS and ANSYS HFSS to assess the scheme proposed from two aspects. The parallel equivalent circuit can be optimized by a similar approach. Then, a WPT system is established in HFSS to further verify the feasibility of miniaturization. Finally, the dimension of the coil antenna can be reduced by about 70%, and its impedance bandwidth can be increased by approximately 40% after two electronic modules are integrated.

Key Technology of Mixed Matching Circuit for Miniaturizing Dual-Band Antenna

“…For example, multi-band filtering techniques have been reported to deal with the signal noise, but it cannot be applied widely because of the disadvantages of massive load loss compared with normal filter [1]- [3]. Later, series of excellent matching blocks based on parameter extraction for two complex impedances were demonstrated by the Smith chart [4] [5]. Although, sufficient theoretical results about the lumped LC resonant circuit have been achieved, few applications based on them were illustrated except load matching [6].…”