A Method of Measuring Gain in Liquids Based on the Friis Transmission Formula in the Near-Field Region

Nozomu ISHII; Takuhei AKAGAWA; Ken-ichi SATO; Lira HAMADA; Soichi WATANABE

doi:10.1093/ietcom/e90-b.9.2401

A Method of Measuring Gain in Liquids Based on the Friis Transmission Formula in the Near-Field Region

Nozomu ISHII, Takuhei AKAGAWA, Ken-ichi SATO, Lira HAMADA, Soichi WATANABE

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In the 300 MHz to 3 GHz 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 3 GHz, 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.

Publication: IEICE TRANSACTIONS on Communications Vol.E90-B No.9 pp.2401-2407

Publication Date: 2007/09/01

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Online ISSN: 1745-1345

DOI: 10.1093/ietcom/e90-b.9.2401

Type of Manuscript: Special Section PAPER (Special Section on 2006 International Symposium on Antennas and Propagation)

Category: Measurements

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Nozomu ISHII, Takuhei AKAGAWA, Ken-ichi SATO, Lira HAMADA, Soichi WATANABE, "A Method of Measuring Gain in Liquids Based on the Friis Transmission Formula in the Near-Field Region" in IEICE TRANSACTIONS on Communications, vol. E90-B, no. 9, pp. 2401-2407, September 2007, doi: 10.1093/ietcom/e90-b.9.2401.
Abstract: In the 300 MHz to 3 GHz 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 3 GHz, 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.
URL: https://global.ieice.org/en_transactions/communications/10.1093/ietcom/e90-b.9.2401/_p

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@ARTICLE{e90-b_9_2401,
author={Nozomu ISHII, Takuhei AKAGAWA, Ken-ichi SATO, Lira HAMADA, Soichi WATANABE, },
journal={IEICE TRANSACTIONS on Communications},
title={A Method of Measuring Gain in Liquids Based on the Friis Transmission Formula in the Near-Field Region},
year={2007},
volume={E90-B},
number={9},
pages={2401-2407},
abstract={In the 300 MHz to 3 GHz 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 3 GHz, 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.},
keywords={},
doi={10.1093/ietcom/e90-b.9.2401},
ISSN={1745-1345},
month={September},}

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TY - JOUR
TI - A Method of Measuring Gain in Liquids Based on the Friis Transmission Formula in the Near-Field Region
T2 - IEICE TRANSACTIONS on Communications
SP - 2401
EP - 2407
AU - Nozomu ISHII
AU - Takuhei AKAGAWA
AU - Ken-ichi SATO
AU - Lira HAMADA
AU - Soichi WATANABE
PY - 2007
DO - 10.1093/ietcom/e90-b.9.2401
JO - IEICE TRANSACTIONS on Communications
SN - 1745-1345
VL - E90-B
IS - 9
JA - IEICE TRANSACTIONS on Communications
Y1 - September 2007
AB - In the 300 MHz to 3 GHz 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 3 GHz, 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.
ER -