Scattering matrix can show us quality of the antena link or cable link between the ports.
S11 – return loss, (reflection coefficient, gamma), this parameter tell us how much power is returning from port number 1. For this measure we need only one port vector network analyzer. If this value is equal 0 dB,this means all of the power is returned from port(for example connector)and antenna can not send a power.
Chart S11 of antenna. Antenna is correctly matching in 700MHz. In this point antenna have small return loss.
where: RL- return loss, Pi – incident power, Pr – reflected power
S12 –insertion loss, attenuation – this parameter show us, how many power is transmitted from port 2 to port 1.
where: IL – insertion loss, PT – transmitted power from port 2, PR – received power from port 1
S22– return loss, reflection coefficient, gamma- how many power is returning from port 2.
S21 – insertion loss – how many power is transmited from port 1 to port 2.