2D and Circuit Directive Gain

Directive Gain is the ratio of the radiation intensity at a specified observation angle to the average radiation intensity. For the observation angle (q,f), the directivity is:

The directivity of the abservation angle equation.

where U is the radiation intensity, which is defined as:

Radiation intensity equation.

The average radiation intensity is related to the radiated power by:

Equation for average radiation intensity.

Directivity

Directivity is the maximum value of Directive Gain, or:

Equation for maximum value of directive gain.

Reference

Warren Stutzman and Gary Thiele, Antenna Theory and Design, Wiley, 1981.