Search

In this paper, we have proposed a dispersive formulation of scalar-based meshless method for time-domain analysis of electromagnetic wave propagation through left-handed (LH) materials. Moreover, we have incorporated Berenger's perfectly matched layer (PML) absorbing boundary condition (ABC) into the dispersive formulation to truncate open-domain structures. In general, the LH medium as a kind of dispersive media can be described by frequency-dependent constitutive parameters. The most appropriate numerical techniques for analysis of LH media are dispersive formulations of conventional numerical methods. In comparison to the conventional grid-based numerical methods, it is proved that meshless methods not only are strong tools for accurate approximation of derivatives in Maxwell's equations but also can provide more flexibility in modeling the spatial domain of problems. However, we have not seen any reports on using dispersive forms of meshless methods for simulation of wave propagation in metamaterials and applying any PML ABCs to dispersive formulation of meshless method. The proposed formulation in this paper enables us to take advantage of meshless methods in analysis of LH media. For modeling the frequency behavior of the medium in the proposed dispersive formulation, we have used auxiliary differential equation (ADE) method based on the relations between electromagnetic fields intensities and current densities. Effectiveness of the proposed formulation is verified by a numerical example; also, some basic factors which affect the accuracy and computational cost of the simulations are studied.

A dispersive delay structure (DDS) is a device that creates a specified group delay function over frequency bandwidth. In this paper, the idea of trapping the electromagnetic waves in a feedback loop is proposed to achieve higher group delay swing. The proposed structure includes two transmission lines and two junctions that act as power divider/combiner. The transmission lines can be either dispersive or non-dispersive. The group delay in the proposed configuration is proportional to the injected power into the feedback loop. So, an increase in the group delay swing can be done by improving the junctions or by adding more feedback loops to the structure. Based on this configuration, a novel DDS, using the substrate integrated waveguide (SIW) transmission line, is introduced. According to the experimental results, the proposed device with a relatively compact size creates high group delay swings (9 ns), and its insertion loss is about 7 dB.

The dispersive meshless method with scalar basis function has been successfully applied for analysis of frequency dependent media. However, as scalar based meshless methods are not always divergence-free in the absence of source,inaccurate or even wrong solutions may be found in the results. To overcome this problem, in this paper, a new dispersive formulation of meshless method with vector basis function is proposed for analysis of dispersive materials. The divergence free property of this method improves the accuracy of simulation by eliminating the artificial charges generated due to the numerical analysis. Moreover, the frequency behavior of the dispersive medium is modeled using auxiliary-differential equations (ADE) method. The efficiency and divergence-free property of the proposed method are verified and compared with dispersive meshless method with scalar basis function by a numerical example.