Anuraag Mohan

Pareto optimal design of absorbers using a parallel elitist nondominated sorting genetic algorithm and the finite element-boundary integral method

Microwave absorbing structures have many applications including the lining of anechoic chambers and the reduction of electromagnetic interference. Pareto optimization is an important tool in the design of absorbers, since most absorbers must be designed keeping both performance and economy in mind. In this paper, a new elitist strategy is implemented into the nondominated sorting genetic algorithm (NSGA) to effectively and efficiently design broadband high performance electromagnetic absorbers. The absorbers are analyzed using the finite element boundary integral method, and the optimization is accelerated with parallel processing. Numerical tests demonstrate that the elitist NSGA proposed in this paper converges faster that the standard NSGA and other classical techniques for a wide variety of absorber design problems. Finally, this efficient elitist NSGA is applied to design complex polygonal absorbers. Numerical results not only demonstrate the robustness of the design algorithm, but also reveal some important information and advantages related to absorber designs based on Pareto optimization.

Convergence Properties of Higher Order Modeling of the Cylindrical Wire Kernel

Recent research has proposed new techniques to analyze the cylindrical wire kernel accurately. These techniques assume a circumferentially invariant surface current distribution. Such an approximation is valid for cases where the wire diameter is very small compared to the wavelength and can be used to model wire structures by using higher order bases. This paper performs a higher order analysis of wire antennas using the method of moments (MoM) and examines the variation in error convergence with wire thickness. Numerical results show that fast convergence can be achieved with these bases up to the point where circumferential variations are important

Convergence Properties of Higher Order Modeling of Cylindrical Wire Kernel

Extensive analysis of wire antennas using method of moments (MoM) has been performed over the past decades. Despite the thorough understanding and widespread use of the wire antennas, higher order modeling of wire structures has received little to no attention over the years. This may be because the inaccuracies associated with the classic reduced kernel approach used to analyze wire antennas have precluded the use of higher order basis functions. This paper combines a new method for computing integrating the cylindrical wire kernel with higher order basis functions for the accurate modeling of wire antennas. Numerical results demonstrate the higher order convergence of the approach

A hybrid method of moments-marching on in time method for the solution of electromagnetic scattering problems

This work proposes a new time domain integral equation (TDIE) solution technique that uses a much larger time step than the method of Weile et al.. Specifically, the method presented in the previous work required the discretization of time based upon the highest frequency in the band of interest. In this work, analytic signal theory and Hilbert transforms are used in such a way the temporal discretization can be accomplished based only on the bandwidth of the signal of interest. Finally, it is be seen that the procedure is equivalent to a hybridization of the TDIE technique with the frequency domain method of moments.

Higher order modeling of surface-wire junctions

Electromagnetic analysis of surface-wire structures has numerous applications in the area of electromagnetic compatibility (EMC), circuit simulation and antenna design. The lack of a higher order technique to analyze wire scatterers as well as the lack of suitable surface-wire bases prevented higher order analysis of structures containing surface-wire junctions. Recent research has demonstrated a new technique to perform higher order analysis of wire scatterers. This work will present interpolatory higher order bases for surface-wire junctions and perform Method of Moments (MoM) analysis of structures containing surface-wire junctions. Numerical results show that accelerated convergence is achieved with these higher-order bases. The frequency domain approach can then be extended to perform higher order transient modeling surface-wire junctions using a suitable Time Domain Integral Equations (TDIE) based approach.

Transient Analysis of Wire Antennas using Higher Order Basis Functions

A higher order scheme that uses band limited interpolation functions (BLIF) as temporal basis functions with band limited extrapolation is used to analyze the transient properties of wire antennas. The classical method-of-moments (MoM) technique used to analyze the wire antenna rely on a reduced kernel approach to avoid the singularity associated with filamentary currents. Unfortunately, inaccuracies associated with the reduced kernel approach preclude the possibility of higher order convergence. This paper uses a Duffy-transform based technique to accurately integrate the wire kernel directly, assuming azimuthal invariance of the current