These are definitions and equations for gain, size, and beamwidth for antennas.
Antennas are described by their gain pattern, g, which indicates how the gain is spatially distributed with respect to the antenna coordinate system. The most important parameters are:
• gain - the maximum value of a gain pattern
• beamwidth - the measure of the angle over which the most of the gain occurs
• sidelobes - the amount of gain in off-axis directions
Ideally, you want highly directional antenna patterns with maximum gain over narrow beamwidth with negligible sidelobes.
Gain = Efficiency x (4 x pi x lambda^2) x Area of Antenna Aperture
Where:
lambda = (speed of light) / frequency
Area = a function of antenna type (which is a function of the diameter, d)
Beamwidth = lambda[d x square root(efficiency)]
The STK Help has more information about:
