Design of an X-band dual circularly polarized

offset reflector antenna

Yumeng Zhang, Yong Liu, Yifan Jiang,Wei Hou , Xin Lv

(Beijing Key Laboratory of Millimeter Wave and Terahertz Technology,

Beijing Institute of Technology Beijing, China 100081)

Abstract: A design of compact X-band dual circularly-polarized offset reflector antenna is described for the radar satellite system. The antenna is composed of a metallic reflector and a horn feed. By introducing the septum polarizer in the horn feed, it makes a more compact size for reduced space. Meanwhile, it is easier for the horn feed to reach the far field boundary condition. The offset reflector has obtained the circularly polarized radiation pattern of above 30dB gain, which the side lobe is less than -24dB; The axial ratio of the direction of the maximum radiation is below 1dB. And the two ports isolation is under -20dB at the center of the frequency of 8GHz. This configuration meets the reliability and consistency requirements for the space.

Key words: offset reflector, dual circularly polarization, Altair FEKO, septum polarizer

1 Introduction

Reflector antennas[1] which operate at millimeter and sub millimeter wavelengths are widely used in the telecommunication and high-resolution radars as its high gain and narrow pencil-beam. Meanwhile, with the development of satellite communication and telemetry technology, a single form of polarization cannot meet the requirements of microwave satellites or remote sensors for the demand of tracking and measuring the target in various polarizations. So it urges to utilize the circularly polarized antennas. In the radar communication, circularly polarized antennas can counter the interference of the rain and clouds. In the electronic countermeasures, they radiate right-hand or left-hand circularly polarized electromagnetic waves and the waves can be received by the antennas with any polarization direction so as to catch wide information even in the extreme environments or climates. With the growing number of the remote sensors in the satellite and the enhancement of the resolution, the high speed data transmission in the Satellite-Earth communication has gained an increasing concern. The most challenging