Design of an L-band orthogonal dual-polarized horn antenna with metal grids for microwave radiometer

In order to satisfy the requirements of a microwave radiometer, an orthogonally dual-polarized horn antenna with operating frequency of 1.4 -1.5GHZ is proposed in this paper. In this design, the aperture of the antenna is divided into 3*3 arrays with metal grids to improve beam efficiency. Besides, an orthomode transducer based on the square waveguide stepped impedance matching and waveguide slot coupling theory is developed as the feed structure to combine or to separate two orthogonally polarized microwave signal. The designed antenna has been fabricated and tested. According to the experimental results, the antenna's voltage standing-wave ratio is lower than 1.3, the gain is greater than 16dB, the antenna's half-power beam width is less than 25 degrees, and the sidelobe is less than -20dB.