Summary
International Symposium on Antennas and Propagation
2006
Session Number:2C2b
Session:
Number:2C2b-4
A Gain Measurement in the Liquid Based on Friis Transmission Formula in the Near-Field Region
Takuhei Akagawa, Nozomu Ishii, Ken-ichi Sato, Lira Hamada, Soichi Watanabe,
pp.1-6
Publication Date:2006/11/2
Online ISSN:2188-5079
Summary:
In 300MHz-3GHz, a probe used in measuring SAR (Specific Absorption Rate) of the mobile communication device is usually calibrated by use of a rectangular waveguide filled with the tissue equivalent liquid. Above 3GHz, however, this conventional calibration has the possibility of inaccurate assessment because the diameter of the probe is comparable with the cross-sectional dimension of the waveguide. Therefore, an alternative calibration for the SAR probe based on another principle is required and is developed by the authors. In our proposed calibration, first, the gain of the reference antenna in the liquid is evaluated by use of two antenna method based on the Friis transmission formula in the conducting medium, and then the electric field radiated by the reference antenna is related to the output voltage of the SAR probe at a point in the liquid. However, the fields are significantly reduced in the liquid and the gain is impossible to be calibrated in the farfield region. To overcome this difficulty, the Friis transmission formula in the conducting medium is extended in the near-field region. In the paper, some numerical and experimental results of estimated gain based on the Friis transmission formula in the near-field region are reported and the validity of the new formula is checked.