Antenna Types – Isotropic Antenna

An isotropic antenna (isotropic radiator) is a hypothetical antenna that radiates equal signal power in all directions, often compared to an incandescent lightbulb. It is a mathematical model that is used as the base of comparison to calculate the directionality or gain of real antennas. No real antenna can have an isotropic radiation pattern, but the isotropic radiation pattern serves as reference for comparing the radiation intensity of other antennas, regardless of type.

An “isotropic antenna” should not be confused with an “omnidirectional antenna“; an isotropic antenna radiates equal power in all three dimensions, while an omnidirectional antenna radiates equal power in all horizontal directions, with the power radiated varying with elevation angle, but decreasing to zero along the antenna’s vertical axis.

Nearly isotropic antennas can be constructed using multiple small elements, and are used as reference antennas for testing other antennas and for field strength measurements, and for backup antennas on satellites which work without the satellite being oriented towards a communication station.