Physical Optics Modeling of AMC Checkerboard Surfaces for RCS-Reduction and Low Backscattering Retrodirective Array
Artificial magnetic conductor (AMC) surfaces have the unique electromagnetic property that the phase of the reflected fields imitate those of perfect magnetic conductors (PMCs). When a perfect electric conductor (PEC) and an AMC surface are placed on the same plane and illuminated by a plane wave, destructive interference occurs between the fields (due to 180 degrees phase difference between the reflected fields of each surface).
In this dissertation, a design procedure is introduced where a refined algorithm is developed and employed on single-band AMCs leading to a 10-dB RCS-reduction bandwidth of 80%. The AMC circuit model is judiciously utilized to reduce the substrate thickness while simultaneously increasing the bandwidth of the AMC surfaces. Furthermore, dual-band AMC surfaces are synthesized and utilized in combination with single-band AMC surfaces to extend the 10-dB RCS-reduction bandwidth from 80% to about 99%. Employing the proposed design procedure, a 99% bandwidth of 10-dB RCS-reduction bandwidth is achieved while reducing the thickness of the substrate by 20%.
The second topic of this dissertation aims at analytically modeling the scattering of planar checkerboard surfaces. The high-frequency asymptotic method, Physical Optics (PO), is utilized to analyze the scattering characteristics of complex structures since the PO is computationally efficient and provides intuitive physical insight. Closed-form formulations developed using PO are used to predict the scattering patterns of checkerboard planar surfaces. The PO-based data compare well, along and near specular directions, with simulations by the full-wave Finite Element Method (FEM).
Finally, a Van Atta retrodirective reflector with low backscattering is designed and developed using a microstrip antenna array. Conventional retrodirective reflectors are sensitive to interference by the fields scattered by the antenna structure. By using a virtual feeding network, structural mode scattering is identified and canceled using AMC technology.