Research On The Innovative RCS Reduction Technologies Of Microstrip Antennas

With the rapid development of the modern information technology, the battlefield survivability and undetectable abilities of the traditional weapons and equipments are face with increasingly serious challenges. In order to tackle those threats effectively, low-observable military platforms are becoming a paramount technology for giant powers. The antenna system, acting as one special scattering object, has tremendous impact on the scatterring performance of the low-observable platform. Although the shaping and loading RAM(radar absorbing materials) technologies can reduce antenna RCS in different degree, they will deteriorate the radiation performance of the antenna. Therefore, the traditional RCSR technologies can not be applied for RCSR of antenna in that its radiation performance cannot be preserved at the same time. Thus, reducing antenna’s RCS as much as possible while preserving the radiation performance becomes a thorny problem for a low-observable platform. Based on the above mentioned problem, this thesis is aim at reducing the RCS of the microstrip antenna by using new technologies with the radiation performance preserved at the same time. The author’s major contributions are outlined as follows:1: As one special scatterer, antenna scattering field consists of the structural mode scattering and antenna mode scattering, which result in the extremely complex scattering mechanism. The scattering theory of antennas is introduced at the beginning of this thesis and some traditional RCSR methods are summarized. The scattering theory introduced in this part provides a solid theoretical for the following RCS reduction contents in this thesis.2: AMC(artificial magnetic conductor), as one of the new artificial materials, is well developed in recent years. Due to its high-impedence characteristic, AMC is widely applied to design the low-profile antenna and reduce antenna’s RCS. As a resonant structure, AMC can not be used to reduce antenna’s RCS over a wide frequecy range because of its narrow operating bandwidth. In order to overcome this drawback, a hybrid AMC structure is proposed in this thesis. This technique can achieve RCS reduction of the microstrip antenna over the frequency range of 4-12 GHz by arranging two different AMC units resonating in two different operating frequencies.3: Compared with the out-of band RCS reduction, the in-band RCS reduction for antenna is much more difficult. The main reason is that the in-band RCS is related to the radiation performance of microstrip antenna. Considering this practical circumstance, the possibility of using microstrip resonators to reduce the in-band RCS of the microstrip patch array antenna is discussed in this thesis. The simulated and measured results show that this method can reduce the in-band RCS to a great degree and the radiation performance of the microstrip antenna is not influenced obviously. This method has the advantage of simple structure compared with the traditional technologies.4:Gradient-index metasurface is one of the novel artificial metamaterials which are developed in recent years. This metasurface can exhibit PW-SW conversion and anomalous refelction characteristics by reasonably design the phase response of the metasurface. The Jerusalem cross elements are employed to design the gradient-index metasurfaces in this thesis, and the RCS of the microstrip slot array antenna is reduced over the frequency range of 6-18 GHz by using the PW-SW conversion and anomalous reflection characteristics. Compared with the traditional RCSR methods, this technique can reduce the in-band and out-of band RCS simultaneously and preserve the radiation performance of the microstrip slot array antenna.