L-Band Circularly Polarized Active Electronically Steered Array Antenna System for a GPS Base-station

This mouthful was designed as part of a final project, that while not a thesis level amount of work, was a more interesting antenna design implementation. The restriction being that I had to design this specifically with circular patch antennas I would also need to design, to compete and compare with a helical and spiral antenna array my classmates would also design. This necessitated three parts that required extra attention, the feed for circular polarity, the antenna design, and the array design, but these also make the design more unique than the results that would be spit out of a textbook.

I was locked into utilizing a circular patch, which traditionally is fed via an offset center point in order to adjust for directionality. My idea, was to instead split the feed into four points that would be progressively phased shifted clockwise or counterclockwise. This meant however that the design had to also incorporate the feed network itself into the same simulation as per the professor’s requirements. To achieve this, I implemented a fixed butler matrix that provided 1 input and 4 progressive outputs with coaxial tubing tuned to the specific center frequency I was targeting, and adjusted to increase overall bandwidth. As I did not have to fabricate it, this design proved rather effective in increasing the circular polarization while also being broadband capable. From this, several arrays were simulated, but mainly as a result of ram restrictions my final array design was simply planar in format, 3×3 setup maximizing broadband radiation with limited 10 degrees scanning capability while maintaining reliable gain