RCS Reduction Of Quasi-yagi Antenna

In the rapid development of electronic technology days, for meeting the needs of the high-tech war, countries around the world have been researching on all kinds of stealth technology to enhance the combat capability and survival ability of soldiers and weapon equipment. In recent years, the countries of the world, especially the United States, Russia, Britain, France and other military powers have stepped up studying of stealth technology. Antenna is a device that accepts and launches electromagnetic, as one of the indispensable equipment on weapon platform, it is also an important factor causing the scattering, so researching stealth of antenna and preserving its good radiation performance at the same time is an important and complex issue.Quasi-Yagi antenna is an antenna with planar structure, it inherits the high gain, wide band, good directivity and low cost performances of the traditional Yagi-Uda antenna, and has the advantages of simple structure, small size, good directionality, low profile and ease of integration etc, so it has been widely used in communication. In addition, because of that the mirror scattering direction of the Quasi-Yagi antenna perpendicular to the maximum radiation direction, Quasi-Yagi antenna is a good choice for low RCS phased-array antenna. With the development of electromagnetic stealth technology, target recognition and radar technology is developing in the tendency of the wide band, so radar stealth technology also needs to meet the requirements of wide band, therefore, the researching of RCS reduction of Quasi-Yagi antenna has important military significance and broad prospects for development.This paper introduces the theoretical analysis and designing method of Quasi-Yagi antenna, with these basic knowledge, a Quasi-Yagi antenna working in the band of 5 GHz- 8 GHz is designed as a reference antenna. On the basis of the reference antenna, arrow-Koch shape dipoles are designed as director and driver of the Quasi-Yagi antenna, and then according to the different current distribution of the radiation state and scattering state on the reflector ground of the Quasi-Yagi antenna, some area of the reflector ground is cut to reduce RCS. Finally, a Quasi-Yagi antenna with low RCS and good radiation performance is designed.In order to achieve the RCS reduction of the Quasi-Yagi antenna with reflect plate, themethod of loading radar absorbing material(RAM) is taken into account. the absorbing bandwidth of the traditional RAM is too narrow to cover the working frequency band of Quasi-Yagi antenna, so useing traditional RAM alone is hardly to achieve the in-band RCS reduction of Quasi-Yagi antenna. In order to solve the problem, this paper designs a broadband composite RAM with frequency selective surface(FSS), the composite RAM has wider absorbing bandwidth and better absorption performance than the traditional one.The novel wideband composite RAM with FSS proposed above is designed to replace the metallic reflect plate of Quasi-Yagi antenna. Compared to the Quasi-Yagi antenna with metal reflect plate, the one with wideband composite RAM has lower monostatic RCS in the working frequency band, and the radiation performance of the antenna is preserved well at the same time. Finally the experiment and simulation results show that the application of wideband composite RAM is effective in RCS reduction of Quasi-Yagi antenna.