The standard rectangular horn antenna is one of the simplest and probably the most widely used microwave antenna and its existence and early use dates back to the late 1800s. A simple and effective way of exciting high purity left- or right-hand circular polarization using a single feed, is by the addition of a septum polarizer into the square feed waveguide.Side cut plane view of the antenna.
The pin-fed square septum horn may be designed for an input impedance range from 50 to 150 Ω, while the gain can vary between approximately 10 and 24 dBi.
The following graphs show typical S11, gain and radiation performance for a left-hand circular 14 dBi design.Typical gain and S11 vs normalized frequency with a reference impedance of 100 Ω. Total normalized left- and right- hand circular gain patterns.