Research Of Microstrip Reflectarray Antenna

Due to its properties of high gain, strong directivity, light weight, and flexibility, reflectarray antenna is rapidly becoming an attractive hotspot in the antenna field. Researches on the analysis of the reflectarray elements and arrays have been done in this dissertation. Major studies of the dissertation are as follows: In Chapter 1, the research background of this dissertation is presented. Firstly, the operational principle of reflectarray antenna and classical elements are introduced. And then its development history and recent advancements are reviewed. Finally, the main works and framework of this dissertation are outlined.In Chapter 2, the analysis techniques used in the following chapters are illuminated, including analysis the phasing characteristic of the elements and the phase distribution design on the array. Based on the comparison of the existing element-analyzing techniques, the waveguide simulator technique is employed to investigate the phasing characteristic of the classical elements, so as to provide guidance for the design of the new elements. In the second part of Chapter 2, a novel phase compensation technique for the horn is presented. This technique can reduce the phase error introduce by the instability of horn’s phase center farthest.In Chapter 3, the research is focused on the broadband technique about reflectarray. The main limitation to reflectarray performance is the narrow bandwidth, generally lower than 5%。Such limitation has already become a choke point to prevent reflectarrays from evolveing towards the direction of high-capacity and multifunction. Firstly, the factors to limit the bandwidth and corresponding solutions are given. Then two new broadband radiating elements are designed. The performances of such new elements are analyzed detailedly and corresponding equivalent circuit model is presented. Simulations and measurement results show that a 1-dB gain bandwidth of 17.2% and 25.2% are obtained.In Chapter 4, the application of frequency-selective surface (FSS) in reflectarray antennas for the purpose of reducing radar cross section (RCS) level and improving gain is investigated. The factors affecting the RCS and gain are given together with the corresponding solutions. Then a FSS ground is chosed to replace the solid ground for above purpose.Different from previous reports, the presented band-stop FSS structure is also characterized by the suppression of surface waves, which makes a contribution to better radiation performance. Two 14x14 reflectarray antennas backed on the FSS ground and a solid ground are designed and fabricated. Simulated and measured results show that the FSS ground can improve the‘in-band’gain by 1.1dB, decrease the sidelobe level by 6.4dB, and reduce the‘out-of-band’RCS effectively when compared with the antenna with a solid ground plane of the same size.In Chapter 5, an‘element-in-array pattern’analysis technique is described. This technique can compute the far field pattern of reflectarray, including mutual coupling effects without having to perform a full-wave simulation to the whole structure, which is usually unfeasible for very large arrays. The approach is based on the scattered field as calculated directly from the induced currents on the center element aperture of a series of much smaller arrays (subarrays) having configurations locally identical to the corresponding parts of the original array. In the numerical example, the proposed method yields the results that show a better agreement with the full wave MoM solution, compared with the traditional‘infinite periodic array’approach and the‘isolated element’approach.In Chapter 6, the research work of this dissertation is summarized and the future works are predicted.