The Design Of A Five-unit Monopulse Radar Antenna At Ka-band

Monopulse antenna plays an extremely important role in aviation,missile defense and other fields because of its outstanding advantages in effective distance,angle and distance measurement accuracy,angular resolution,the ability of tracking moving target and anti-interference. This paper proposes a kind of monopulse radar seeker antenna used in engineering practice at Ka-band.This paper presents a monopulse antenna with a feed-forward parabolic structure.According to the design requirements: the antenna's VSWR should be less than 1.6, the gain should be higher than 28 d Bi?the isolation between sum and difference below-20 d B?sidelobe level lower than-17 d B?beam width less than 4.8°and zero depth lower than 35 d B.For the simple structure of the paraboloid and less performance parameters,this paper focuses on the feed design. Two structuresfour-unit feed and five-unit feed with waveguide to coaxial transitional formsare designed and simulated using HFSS of which the result meets the requirement well. Because the final engineering requirements need five roads transmission, only five-unit squre waveguide feed is fabricated and tested.The result presents that: the VSWR is lower than 1.4, the isolation between sum and difference port is lower than-20.3d B, the gain is higher than 28 d Bi over 34.7GHz,35 GHz,35.3GHz and the sum beam sidelobe level is less than-17 d B at the azimuth and elevation plane except the azimuth over the 35.3GHz. After analyzing the test result, we can adjust the location of the feed caliber to improve the antenna performance. The agreement between test result and simulation result verifies the practicality of this design.