Research On Analysis And Control Methods Of Antenna Radar Cross Section

In the modern war with complicated electromagnetic environment, the stealth performance of the weapon target (such as aircraft) directly determines its battlefield survival probability and penetration ability. With the rapid development of stealth technology, the radar cross section (RCS) of a target has been better controlled. For these low observable platforms, the RCS from an antenna often becomes a bottleneck, which restricts the stealth effect of the whole system. Therefore, effectively control the antenna RCS and reasonably relieve the contradictions between the radiation demands and the scattering requirements have great guiding significance for the stealth design of a target. Being associated with the research project, this dissertation is mainly concerned with the antenna RCS analysis and control methods, the author's major contributions are outlined as follows:1. The antenna scattering mechanism is analyzed, and the results of the structural mode and the antenna mode scattering from different antennas are given. To achieve the antenna RCS control, the method of moments (MoM) has been studied. The antenna radiation and scattering parameters, especially the result of the antenna mode scattering are calculated by MoM. Meanwhile, in order to overcome the problem of MoM excessive storage, the adaptive integration method (AIM) is discussed, and the RCS calculation results and relevant analyses of the electrically large objects are presented.2. The antenna RCS reduction is virtually a compromise process among various conflicting requirements. Therefore, this dissertation adopts optimization algorithms to control the antenna scattering and achieve the antenna design of low RCS. The contradiction between the high radiation performance and low scattering effect is better balance through the design of the objective function.3. In the optimization process, the differential evolution (DE) algorithm and particle swarm optimization (PSO) algorithm are investigated and used to control the antenna RCS. To improve the design efficiency of the antenna array, this dissertation discusses the space mapping (SM) method, and combines the implicit space mapping (ISM) strategy with differential evolution algorithm. In this process, the coarse model with high speed and fine model with high accuracy are established. The parameter extraction course is designed to find the mapping relationship between these two models. This mapping relationship is optimized by DE, so that the coarse model can continuously approach the fine model. At last, the optimization speed and calculation accuracy are improved together. 4. The forming reason of RCS peak from the microstrip antenna is analyzed through the discussion of the surface current excitated by incident wave. It shows that the RCS resonance peak of a microstrip antenna is closely related to the resonance mode of antenna surface current, which provides a basis for RCS reduction of a microstrip antenna. Therefore, through the optimization method, this dissertation finds the best slot locations, in which the scattering resonance modes are restrained but the antenna operation mode is almost unchanged. The method of slotting can cut off or weaken the resonance current of non-radiation mode, thus a batter RCS reduction effect is obtained.5. The frequency selective surface (FSS) has been studied, and a small size bandstop FSS with regular hexagon structure is proposed. This FSS is designed according to the space-filling characteristics of fractal structure. The FSS array adopts the equilateral triangle arrangement and has good angle stability. Using this FSS as antenna reflector, in the antenna operating band, this structure performs the bandstop characteristic and works as a metal plate. While outside the operating band, this design shows the bandpass characteristic, so that most of the incident energy passes through the antenna and is absorbed by the absorbing material behind the antenna. Therefore, the antenna radiation is ensured and the RCS is reduced.6. The application of array synthesis method in antenna RCS control is proposed. By optimizing the spatial location of array element, the structure mode scattering from array antenna is restrained. By loading a group of delay lines with different length between the array elements and the feed network ports, the phase difference between the array radiation and the antenna mode scattering can be amplified artificially. Optimizing this phase difference, the antenna mode RCS from array antenna can be controlled.7. The secondary development of HFSS software is proposed. The VB scripts for antenna radiation and scattering problems are compiled by Matlab software. And then, these VB modules are operated by optimization algorithm. The candidate antenna models to be optimized are calculated by calling HFSS software. By this method, finally, a UWB antenna with dual band-rejected characteristic and a 4×2 microstrip conformal array antenna with low RCS effect are successfully designed.