Varsha Mishra

A new method is outlined in this manuscript to design an optimized microwave absorber (MA) achieving the desired level of reflection bandwidth (RBW) and surface wave attenuation (SWA). The proposed semianalytical two-dimensional dynamic method is best suited for the type of MAs consisting of either single-layer or multilayer impedance surfaces, such as resistive sheets and meta-materials. The proposed work contains the following two aims: 1) computation of the SWA in meta-material-based absorbers and 2) optimization of MA parameters for obtaining the desired level of SWA and RBW. To achieve the first aim, a complete mathematical explanation is outlined in detail, and further, to validate it, a particular example is implemented through which it is possible to simulate and analyze the structure via full-wave simulations. This proposed methodology is further integrated with the multiobjective optimization process of a genetic algorithm to achieve the second aim. Consequently, optimization of MA parameters is carried out and the desired level of outputs (i.e., RBW and SWA) is achieved. The proposed approach is explained by means of various examples of MAs and after detailed analysis, some competitive solutions are achieved. The proposed work can be widely applied in microwave frequency-based electronic devices to avoid surface electromagnetic wave coupling.

In the application of oil-spill monitoring, the satellite revisit time needs to be as short as possible to identify minor spills before they can cause widespread damage. Simultaneously, it is required to capture a sufficient amount of information about the surface to clearly distinguish between oil-spilled and oil-free sea regions. The Hybrid-polarimetry (hybrid-pol) synthetic aperture radar (SAR) system can be exploited for such capabilities. However, limited hybrid-pol based oil-spill descriptors are reported in the literature in comparison to rich sets of full-polarimetry (full-pol) based descriptors. In this letter, we establish a direct relation between hybrid-pol data and full-pol data under reflection-symmetry condition. Consequently, through the proposed work, the rich sets of full-pol based oil-spill descriptors can be derived directly from the hybrid-pol datasets. For the validation of the proposed work, L-band ALOS PALSAR and UAVSAR datasets acquired over the Gulf of Mexico have been used.

A methodology for analyzing the attenuation constant of surface wave propagating in general multilayer structures is proposed. The multilayer structure may include any number of layers, that can be made up of lossy dielectric, magnetic-material, and impedance surfaces. The non-linear characteristic equation (transverse resonance equation - TRE) of the multilayer structure is defined by utilizing transmission line (TL) theory. Consequently, the root(s) of the TRE is/are computed which indicates the complex propagation constant of that characteristic equation. The obtained results are validated over the completely shielded waveguide structures where the full wave simulation is possible. The proposed approach is employed to analyze and discuss the propagation and attenuation constant of surface wave modes in several representative examples. The analysis is carried out in the frequency range from 1 to 12 GHz.