Research On The Microstrip Antennas And Their Arrays With Low In-Band RCS

Analysis and computation of Radar Cross Section (RCS) is one of the important topics in electromagnetic scattering research. To meet the demands of rapid development of electronic and information warfare, the reduction of the antenna’s RCS is of great significance and therefore receives a lot of attentions. This dissertation aims to reduce the in-band RCS of antenna simultaneously without degrading the radiation performance. Based on the scattering theory of antenna, the relationships between antenna in-band scattering property and the antenna structure are carefully investigated. Based on them, several effective solutions have been developed for RCS reduction of antenna.The main work and innovation points of this dissertation are concluded as follows:1. Investigations on the radiation and scattering mechanism of linear dipole antenna, spiral dipole antenna and planar spiral dipole antenna show that even different structures may achieve similar radiation performance but with a significant difference in scattering property. This is the theoretical bases of this dissertation. Furthermore, it is found that changes in antenna structure may result in significant differences in their near-field property (the EMC property). Therefore, trade-offs should be made among radiation, scattering and near-field performances in the antenna design.2. Investigation of the inherent scattering (structural model scattering) of microstrip antenna shows that the frequency point for inherent scattering resonance is not always coincident with the that for radiation resonance. Changing the location of feed point is proposed for changing operating frequency of the antenna so as to make the radiation and scattering resonance happening at the same frequency point. As a result, the in-band antenna RCS is largely reduced. In addition, two modified symmetric feeding configurations are proposed to suppress cross-polarization level while maintaining lower in-band scattering property of the antenna.3. A novel kind of composite patch antenna is proposed. In the design, the mushroom-like electromagnetic band-gap (EBG) structure is integrated onto the conventional patch. This new structure combines the patch and EBG as a whole and effectively reduces the in-band RCS yet without sacrificing the radiation performance and antenna size. Furthermore. The introduced EBG structure leads to a broader operation band for the antenna.4. An approach for reducing the antenna in-band RCS by using slotting in the ground plane is proposed. The microstrip antenna and microstrip array are studied. In addition, the approach for suppressing the backward radiation caused by the slots in the ground plane is proposed by adding quarter wabelength cavities backed on the slots. The results show that cavity-backed slots can reduce antenna RCS in a certain angle range of broadside direction with little effects on antenna radiation performance.5. Based on the structure of sparse array antennas, the approach using passive cancellation technique is proposed for in-band RCS reduction, which exploits the scattered field generated by a non-radiating element to cancel the scattered field generated by a radiation element. This approach is applied to the sparse array antenna, and simulation results validated its efficiency of reducing the in-band RCS of antenna.