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A Method of Measuring Gain in Liquids Based on the Friis Transmission Formula in the Near-Field Region(Measurements,<Special Section>2006 International Symposium on Antennas and Propagation)
Ishii, Nozomu
Akagawa, Takuhei
Sato, Ken-ichi
Hamada, Lira
Watanabe, Soichi
Copyright (C) 2007 IEICE
本文データは学協会の許諾に基づきCiNiiから複製したものである
Friis transmission formula
SAR probe calibration
conducting medium
Fresnel approximation
far-field gain
In the 300MHz to 3GHz range, probes used to measure specific absorption rate (SAR) of mobile communication devices are usually calibrated using a rectangular waveguide filled with tissue-equivalent liquid. Above 3GHz, however, this conventional calibration can be inaccurate because the diameter of the probe is comparable to the cross-sectional dimension of the waveguide. Therefore, an alternative method of SAR probe calibration based on another principle was needed and has been developed by the authors. In the proposed calibration method, the gain of the reference antenna in the liquid is first evaluated using the two-antenna method based on the Friis transmission formula in the conducting medium. Then the electric field intensity radiated by the reference antenna is related to the output voltage of the SAR probe at a given point in the liquid. However, the fields are significantly reduced in the liquid, and the gain is impossible to calibrate in the far-field region. To overcome this difficulty, the Friis transmission formula in the conducting medium must be extended to the near-field region. Here, we report results of simulations and experiments on estimated gain based on the extended Friis transmission formula, which holds in the near-field region, and test the validity of the new formula.
電子情報通信学会
2007-09
eng
journal article
VoR
http://hdl.handle.net/10191/25749
https://niigata-u.repo.nii.ac.jp/records/1803
http://doi.org/10.1093/ietcom/e90-b.9.2401
http://ci.nii.ac.jp/naid/110007541051
AA10826261
0916-8516
IEICE transactions on communications
E90-B
9
2401
2407
https://niigata-u.repo.nii.ac.jp/record/1803/files/110007541051.pdf
application/pdf
1.3 MB
2019-07-29