# How would I calculate aperture efficiency for an antenna?

How to calculate aperture efficiency for an antenna with the following parameters:

• Big reflector diameter= 24 mm
• Gain= 9.265 dbi
• Frequency= 11.60 GHz
• 24mm? Did you mean cm? – Phil Frost - W8II Oct 14 '19 at 16:04

For any antenna, also for wire antennas, you can calculate so called effective area with $$A_{eff} = \frac{\lambda^2}{(4\pi)}G$$. An ideal antenna with surface area of $$A_{eff}$$ absorbs the same amount of power from the plane wave as that antenna. Aperture efficiency is defined as ratio of effective and physical surface area $$\eta_{ap} = A_{eff}/A_{phys}$$. For a circular reflector antenna the physical size is the area of your antenna facing the incoming plane wave $$A_{phys} = \pi(d/2)^2$$.