Engineering Tutorials

Consider a dish antenna pointed at an isotropic antenna transmitting some distance away. We know that the isotropic antenna radiates uniformly in all directions, so it is a simple matter of spherical geometry to calculate how much of that power should be arriving at the dish over its whole aperture . Now to measure how much power is being received from the dish (at the electrical connection to the feed) – never greater than is arriving at the aperture. The ratio of power received to power arriving is the aperture efficiency.

The total antenna efficiency accounts for the following losses:

(1) Reflection because of mismatch between the feeding transmission line and the antenna and
(2) Antenna conductor and dielectric losses.