الفهرس 
الغلافOnly 14 pages are availabe for public view
 |  | from | 233 |  |  |
| | | from | 233 | | |
Abstract
ABSTRACT
This thesis presents basic theory and detailed analysis of electromagnetic (EM) wave material absorbers and/or target shaping with their applications in different target radar cross section reduction (RCSR). Therefore, EM stealth technology has been discoursed for reducing the radar cross section (RCS) over varieties of targets and different angle of incidents based on two foremost techniques, radar absorbing material (RAM) and target shaping. The purpose of studying targets RCS is to assess their effect on the performance of radar communication systems. Several RCSR methods are modeled, analyzed, optimized throughout powerful computational methods that affect their accuracies, convergences and then cite their merits and demerits.
The RAM’s even conventional, meta-surfaces or circuit analog radar absorbing (CAR) types represent three-dimensional (3-D) forms from natural and/or synthetic materials. The radar target shapes have many forms including both 2-D and three dimensional (3-D) with either metallic or coated bodies. Different material electrical, magnetic properties and/or geometric parameters are widely used within both technologies.
The interactions of EM fields thru the double-layer structure geometries have been studied through the forward/backward propagation approach. Moreover, related forward-backward propagation approach with either homogenization or equivalent circuit model (ECM) mathematical expressions is considered respectively in case of arbitrary shaped object, meta-surfaces and CAR absorber material.
In this thesis, efficient lightweight double-layer absorbers with impedance-matching structure at X-Ku bands are designed and implemented firstly using Genetic Algorithm (GA). Then improving the RCSR of a manufactured compact double - layer (RAM) is presented to enlarge the operating bandwidth to include K band besides X, Ku bands. The EM wave absorption for wide varieties of incident angles up to 60oand both polarization types TE/TM are also studied. To increase the band-stop resonating frequency up 26 GHz and 50o incident angles, an additional planar layer of meta-surface, circuit CAR, or a thin RAM layer is engineered. The effects of the dielectric losses especially on the impedance of CAR or high impedance structures (HIS) resulted in meta-surface
iv
layer are analysed using the ECM method. Raising the incident angle ranges up to 60o is presented by monitoring the RCS performance in the desired frequency bands through three altered structures. Firstly, a shaping structure of uncoated periodic honeycomb is combined to the manufactured doubled layer RAM. Then, a periodic coated honeycomb composite structure is used only with a complete analysis of its effective EM material properties expressions. Finally, radar absorbing structure (RAS) of three layer absorbers is offered through manufactured another planner thin RAM using the extracted effective EM material properties of a periodic coated honeycomb composite. The GA is considered throughout all approaches to optimize the material properties and thickness for better absorption of the incident EM wave.