# Calculating Antenna Gain

As far as I understand, and antenna like a simple dipole has a circular radiation pattern at the 2 edges, so the physical aperture in this case is circular.

$${A = \pi * r^2}$$

Where r is the radius of the circle surrounding the dipole, or basically r is the length of 1 rod of the dipole.

Then we have the gain formula:

$${G = 10* \log_{10} ( \frac{\eta * 4 * \pi * A }{\lambda ^2 } )}$$

Where eta is the efficiency, and A is the aperture calculated above.

So can we use the following formula to calculate the gain of an antenna?

$${G = 10* \log_{10} ( \frac{\eta * 4 * \pi^2 * r^2 }{\lambda ^2 } )}$$

• What do you mean by aperture. My version of aperture involves wavelength. Jun 10, 2017 at 12:19
• @Andyaka I meant physical apperture which is defined by the smallest circle surrounding the antenna. There is also the "antenna aperture" definition which contains also the nearby area where the current can couple to other objects and relay the signal to the antenna. Jun 11, 2017 at 13:04
• what happens if I increase the aperture size what is the effect on gain/directivity?? PS sorry....i can't comment this post, i don't have 50 point
– user193562
Jul 26, 2018 at 8:28