Design of antenna feed for mono-pulse auto-tracking ground station

An S-band auto-tracking antenna feed for mono-pulse ground station is presented. The uplink band is from 2.025 to 2.12 GHz and the downlink band is from 2.2 to 2.3 GHz. The feed is utilized to modify the orientation angle of the antenna to align antenna boresight with a satellite. According to the mono-pulse radar theory, the system structure can be divided into two parts, sum and difference channels. Sum channel is used for data transmission and the key component is a septum polarizer which generates circularly polarized electric fields. Difference channel is used to modify the antenna angle and the key component is a TE21 tracking coupler with signal combining circuits. The results show that the polarization isolation is larger than 40 dB, and the axial ratio is smaller than 1.4 dB.