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In electromagnetics, the antenna factor is defined as the ratio of the electric field strength to the voltage ''V'' (units: V or µV) induced across the terminals of an antenna. The voltage measured at the output terminals of an antenna is not the actual field intensity due to actual antenna gain, aperture characteristics, and loading effects. For an electric field antenna, the field strength is in units of V/m or µV/m and the resulting antenna factor ''AF'' is in units of 1/m: : If all quantities are expressed logarithmically in decibels instead of SI units, the above equation becomes : For a magnetic field antenna, the field strength is in units of A/m and the resulting antenna factor is in units of A/(Vm). For the relationship between the electric and magnetic fields, see the impedance of free space. For a 50 Ω load, knowing that PD Ae = Pr = V2/R and E2=377PD, the antenna factor is developed as: : Where * Ae = (λ2G)/4π : the antenna effective aperture * G: the antenna gain For antennas which are not defined by a physical area, such as monopoles and dipoles consisting of thin rod conductors, the effective length is used to measure the ratio between E and V. ==Notes== 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Antenna factor」の詳細全文を読む スポンサード リンク
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