12.3.2 Effective Aperture
The power received by an antenna can be associated with a collecting area—the power density incident upon the antenna (in watts per square meter) is converted into a received power (in watts) by multiplying the power density of the received signal by the effective receiving area of the antenna). Every antenna may be considered to have such a collecting area that is called the effective aperture Ae. It can be shown that an antenna with power gain G has an effective aperture Ae at the operating wavelength λ that is given by:
The effective aperture may be associated with a physical aperture, as in the case of a horn antenna, although it is usually smaller. However, even a linear antenna such as the dipole can be associated with an effective aperture even though it has no physical aperture. That is, for a given power density incident upon the antenna, the effective aperture is a measure of how much power is collected by the antenna—an antenna with a larger effective aperture will collect more power.
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