Research On Accurate Scattering Analysis Of Targets And RCS Control Techniques For Microstrip Antennas

Being associated with two research projects, this dissertation is mainly concerned with the electromagnetic computation of targets and stealth techniques for microstrip antennas. Fast and precise scattering computation algorithms for electrically large targets and methods for antenna RCS prediction and reduction are studied. The author's major contributions are outlined as follows:1. Research on array antenna RCS computation. Based on the fundamental theory of electromagnetic computation, the method of synthetical basis function (SBF) is proposed as a fast algorithm of MoM to compute the array antenna scattering. The memory and time limitation of traditional MoM in terms of PC hardware is avoided. Firstly the array antenna is divided into blocks, and each block is subdivided into triangle facets. Secondly the sum of RWG base functions on each block is obtained, which can reduce the number of unknowns thus accelerate the computation speed.2. Precise scattering analysis of electrically large targets by use of AIM. As another fast algorithm of MoM, AIM is deduced in detail. The algorithm improves the scattering computation ability by reducing the storage quantity. The solving method of matrix equation is improved by introducing BICG, which increases the computation speed to a further extent.3. AIM parallel computation for scattering of electrically large targets. In order to enlarge the scale of problem, the AIM parallel computation technique is utilized. The critical point is the parallel modification of impedance filling process and the solving process using BICG. This dissertation analyzed the scattering of electrically large targets and results show the superiority of AIM parallel computation.4. Scattering analysis of microstrip printed dipole antenna. A scattering analysis method of the microstrip printed dipole antenna is introduced. The main aim is to decompose the structural mode scattering and antenna mode scattering of the microstrip printed dipole antenna with feeding structure. The structural mode scattering and antenna mode scattering of antennas loaded arbitrarily can be calculated by setting open and short circuits at the feed point. The scattering of microstrip printed dipole antennas loaded arbitrarily is decomposed, which is the base of RCS reduction of microstrip printed dipole antennas.5. RCS reduction analysis of microstrip printed dipole antennas and arrays. Attention is focused on the broadband and low scattering performances. Firstly the radiation and scattering characteristics of element antenna are analyzed. The PBG structure is introduced to improve the bandwidth of the element antenna. Secondly, the ground size reduction method is proposed according to the scattering performance of the element antenna. Finally a4×2broadband printed dipole array antenna designed using this method has both a favorable radiation performance and low RCS.6. Research on microstrip patch antenna RCS reduction technique. Attention is mainly focused on the RCS reduction of microstrip patch antenna and array. The principle of scattering reduction is discussed in detail. A novel theory of patch antenna array scattering reduction which is named patch antenna element gradually changed slotting is introduced. Slots of different sizes are carried out for different elements, which can realize the low sidelobe characteristic of far field when the array elements are fed uniformly. This technique not only realizes the low sidelobe characteristic of far field, but also realizes the RCS reduction of structural mode scattering into account. On the basis of theory analysis, a 1×9 patch antenna array is designed and experiments show the correctness and practicability of the technique.