An important aspect in link budget calculations, effective aperture, $A_e$ defines the amount of power received by an antenna in relation to the power density of a signal, $p$. The total power received by an antenna is defined as $P=pA_e$. From this definition, it becomes more obvious as to why the term is also commonly known as effective area.

This constant can also be calculated using the following equation:

$$ A_e=\frac{G\lambda^2}{4\pi} $$

where $G$ is the receiver's gain (at its strongest orientation), $\lambda$ is the frequency of the wave, and $A_e$ is the effective aperture.