good morning all,
I have difficulties to find the correct formula that allows me to calculate the gain of half wave dipole in parallel with another parasitic half wave dipole.
I'm trying to calculate the gain(theta,phi) of this array for different distances bentween the two dipoles.
I found the equation $|E_T|$ down below and i want to know how can i calculat the gain frome this equation ?
I'm admitting the reciprocity of the antennas so:
$Z_{21}=Z_{12}$ and $Z_{11}=Z_{22}$.
$\gamma_{12}=\frac{Z_{22}-Z_{0}}{Z_{22}+Z_{0}}$ and $\gamma_{12}=\frac{Z_{12}-Z_{0}}{Z_{12}+Z_{0}}$
$Z_{11}=73.12 +42.54i$
$\beta=\frac{2\pi}{\lambda}$
$E_{T}=\frac{KI_{1}}{r} \sqrt{1+\frac{|Z_{12}|^2}{|Z_{22}|}-2\frac{|Z_{12}|}{|Z_{22}|}\cos(\gamma_{12}-\gamma_{22}-\beta d \cos{\phi\sin{\theta})}}$
I plotted the value of $Z_{21}$ with respect of d (separation distance between the dipoles