Far-Field Gain Estimation of Sandwiched Dipole Antenna in Tissue Equivalent Liquid at 5.2GHz

The authors have studied a technique for calibrating an electric-field probe used in the measurement of Specific Absorption Rate (SAR) for the mobile communication device. The probe can convert electric field intensity radiated by a reference antenna into output voltage in the tissue equivalent liquid. The measurement in the far-field region of the reference antenna is more difficult as the frequency is higher due to highly conducting loss of the liquid. The authors have proposed an extension of the Friis transmission formula which is valid in the near-field region of the antenna, set up the measurement system using a vector network analyzer with an amplifier, and then fitted measured near-field gain to the corresponding theoretical curve to estimate the absolute gain of the reference antenna. In this paper, a sandwiched dipole antenna is used as the reference antenna, and then its absolute gain is estimated at 5.2GHz. The error of measured attenuation constant cannot be ignored in the curve fitting process. A solution to remove the error of the attenuation constant is also described in this paper.