Optimization Of The Tetrapod-Shaped Zinc Oxide Whisher Radar Absorbing Coatings And Mechanism Analysis

In the modern warfare, the information capture and the counter-capture have become a main focus, and the stealth of weapon is able to increase the military benefit significantly. The radar absorbing materials (RAM) are growing quickly, and used widely as a stealth material. Without changing the shape of the weaponry, the coating of RAM is the most economical and efficient way to realize the stealth of radar subjects. Therefore, the optimization design of RAM and the analysis of absorbing mechanism have the vital significance for the stealth and anti-stealth techniques.A new radar absorbing material (Tetrapod-shaped zinc oxide whisker, or called ZnOw) has many good performances, such as the strong adhesion, the light weight, the broadband, and the strong capacity of absorbing electromagnetic waves. Since the special structure and the multiple functions, ZnOw is not only endowed with good absorbing characteristic in microwave band, but also demonstrated excellent overall performance. Consequently, the optimization of the material and the study of the absorbing mechanism will be help to design and prepare this material.Based on the analysis of single-layered radar absorbing coating, we know that it is usually very difficult to satisfy the matched conditions within a frequency band for the RAM. There exist many internal contradictories among the requirements, such as the wideband, the strong absorbing performance, the light weight, and the thin thickness for the actual absorbing coating. In order to obtain the optimal effect, an integrated design is required. The absorbing performance of a single-layered RAM is not good, and the requirements of the RAM are relatively critical. It is very difficult to select a matched RAM for the radar absorbing coating with a limited thickness. Therefore, a multi-layered RAM will be a good choice in order to improve the absorbing effect and to use fully the existing RAM resources.In this dissertation, an optimization design is presented for the multi-layered RAM made of ZnOw based on the microgenetic algorithm (MGA). A fast optimization procedure is designed for a given maximum thickness and the different obsorbing performances for several frequency bands within the range of 2～18GHz. The effects of the thickness, the number of layers, and the restrained conditions on the absorbing performance are discussed in detail. In addition, the different obsorptances are specified for the different bands, and the effect on the optimization is analyzed.A new optimization procedure combining the ant colony algorithm and the microgenetic algorithm is presented for the multi-layered RAM. The optimization procedure is designed in the several frequency bands from 2GHz to 18GHz for the same requirement. The computed results show that this new hybrid algorithm can obtain a solution being better than that of the microgenetic algorithm, and provides a new approach to solve the similar combinatorial constrained optimization problems.The existing theories of the ZnOw RAM's absorbing mechanism are completely summarized, and some exploratory methods analyzing the absorbing mechanism are proposed by the macroscopic and the microscopic respects. The quantum well theory is employed to explain its absorbing mechanism in the several frequency bands from 2GHz to 18GHz.Furthermore, the performance of the multi-layered RAM is strongly related to the thickness and the electromagnetic property of the coatings. In this dissertation, the effects of the errors in the electromagnetic parameters and the thickness of the coatings on the absorbing performance of RAM are discussed based on the optimal results, and especially for the dielectric layer nearby the perfect electric conductor bottom. Finally, some general experimental techniques to measure the electromagnetic parameters of the material and the performance of the radar absorbing coating are introduced briefly.Based on the research work of this dissertation, the optimization technique to design the multi-layered RAM and some optimal results are obtained, and the absorbing mechanism is analyzed as well. All of these results will be a correct guidance for the investigation and preparation of the actual RAM.