A gain calibration in the liquid including the effects of fresnel field and systematic uncertainty

Abstract

One of calibration techniques for electric field probes used in the standardized SAR (Specific Absorption Rate) assessment is based on the Friis transmission formula in the far-field region for the conductive medium. In practice, it is difficult to measure power transmission between transmitting and receiving antennas in the far-field region for the liquid used in the SAR assessment because of its large attenuation. To overcome the difficulty, the authors extended the formula taking into account the Fresnel approximation. The extended formula is valid in the Fresnel region of the antennas for the conductive medium. In this paper, the far-field gain of the antennas can be estimated by not only using the extended formula but also considering systematic uncertainty of measuring power transmission. Adding the effect of the measurement uncertainties can make the resulting uncertainty of the gain small, because the measurement uncertainty of the power transmission largely depends on its level so that this behavior can not be ignored in the liquid.