Performance Evaluation of Built-In Small LF Antennas inside a Metal Case

Kazuaki ABE
Jun-ichi TAKADA

Publication
IEICE TRANSACTIONS on Electronics   Vol.E90-C    No.9    pp.1784-1792
Publication Date: 2007/09/01
Online ISSN: 1745-1353
DOI: 10.1093/ietele/e90-c.9.1784
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Section on Microwave and Millimeter-Wave Technology)
Category: Antennas/Systems
Keyword: 
magnetic core loop antenna,  amorphous metal,  LF,  magnetic field simulation,  

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Summary: 
This paper describes a method for evaluating the performance of a small magnetic core loop antenna used for radio controlled watches. Recently, amorphous metal core loop antennas are used as built-in small antennas inside a metal case. It is difficult to perform electromagnetic simulation for amorphous core loop antennas because of the complicated laminate structure. Therefore, we modeled the amorphous metal core loop antenna as an equivalent bulk structure having anisotropic permeability property that we can simulate. We analyzed the receiving sensitivity of the amorphous antenna by calculating the antenna factor. The receiving sensitivity degrades remarkably when an antenna is inside a metal case. We performed further simulation to investigate eddy current losses that cause deterioration.