Vector Field Transformation for Electromagnetic Scattering

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Solution Overview

Problem

Current methods for calculating electromagnetic scattering properties of periodic structures are computationally burdensome, making real-time reconstruction impractical, especially for complex structures beyond simple one-dimensional periodic structures.

Innovation Solution

A method involving the numerical solution of a volume integral equation for a vector field related to the electromagnetic field, using a change of basis to determine an approximate solution, and representing the vector field with a finite Fourier series, along with convolution operations to determine electromagnetic scattering properties.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If known numerical procedures are used to model scattering, then scattering properties can be determined, but computational burden becomes excessive making real-time reconstruction impractical

Engineering Contradiction:
Improvescattering property calculation accuracyVSAvoidcomputational time
Core Design Contradiction:
Measurement precisionVSLoss of time

Solution Approach 1:

The patent transforms the electromagnetic field parameters by introducing a new vector field F related to E through a change of basis. This parameter transformation converts the original discontinuous electromagnetic field at material boundaries into a continuous vector field, enabling the use of efficient Fourier-based numerical methods that significantly reduce computational time while maintaining accuracy in scattering property calculations

Inventive Principle:
Principle #35Parameter changes

Solution Approach 2:

The patent replaces traditional mechanical numerical procedures with a Fourier-based computational approach. By representing the continuous vector field F using finite Fourier series and utilizing convolution operations in the frequency domain, the method substitutes computationally intensive time-domain or spatial-domain numerical procedures with efficient frequency-domain calculations, achieving real-time reconstruction capability

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

2Measurement precision

If known numerical procedures are used to model scattering, then scattering properties can be determined, but memory usage becomes excessive

Engineering Contradiction:
Improvescattering property calculation accuracyVSAvoidmemory usage
Core Design Contradiction:
Measurement precisionVSQuantity of substance

Solution Approach 1:

The transformation to a continuous vector field F enables the use of spectral methods with Fourier series representation, which require significantly less memory compared to traditional discretization methods. The convolution operations in the frequency domain utilize the convolution theorem, reducing both computational complexity and memory requirements while preserving scattering calculation accuracy

Inventive Principle:
Principle #35Parameter changes

Solution Approach 2:

The patent uses Fourier series to create a spectral representation of the continuous vector field, effectively copying the field information into the frequency domain where operations can be performed more efficiently with reduced memory footprint. This spectral copying allows accurate scattering property determination with minimal memory usage

Inventive Principle:
Principle #26Copying

3Adaptability or versatility

If traditional methods are used for complex structures, then scattering can be modeled, but the structures must be simple one-dimensional periodic structures

Engineering Contradiction:
Improvestructure complexity handlingVSAvoidcalculation speed
Core Design Contradiction:
Adaptability or versatilityVSProductivity

Solution Approach 1:

The change of basis transformation to a continuous vector field F, combined with Fourier series representation, naturally handles complex multi-dimensional periodic structures. The method's formulation in the frequency domain using convolutions is inherently suited for periodic structures of arbitrary complexity, eliminating the one-dimensional limitation while maintaining high calculation speed through efficient spectral methods

Inventive Principle:
Principle #35Parameter changes

Solution Approach 2:

The patent extends the applicability from one-dimensional periodic structures to structures periodic in multiple dimensions by utilizing the Fourier transform's ability to handle multi-dimensional periodic functions. The convolution operations and spectral representation naturally generalize to higher dimensions, enabling versatile modeling of complex structures without sacrificing computational efficiency

Inventive Principle:
Principle #17Another dimension (Dimensionality change)

Data Source

PatentUS8731882B2Methods and apparatus for modeling electromagnetic scattering properties of microscopic structures and methods and apparatus for reconstruction of microscopic structures
Publication Date: 2014.05.20 ASML NETHERLANDS BV
  • US8731882B2 patent drawing
  • US8731882B2 patent drawing
  • US8731882B2 patent drawing

AI summary

Improved convergence in the volume-integral method (VIM) of calculating electromagnetic scattering properties of a structure is achieved by numerically solving a volume integral equation for a vector field, F, rather than the electric field, E. The electric field, E, is determined from the vector field, F, after solving of the volume integral equation. The vector field, F, may be related to the electric field, E, by a change of basis, and may be continuous at material boundaries where the electric field, E, has discontinuities. Convolutions of the vector field, F, are performed using convolution operators according to the finite Laurent rule, which allows for efficient matrix-vector products using Fast Fourier Transforms. An invertible convolution-and-change-of-basis operator, C, is configured to transform the vector field, F, to the electric field, E, by performing a change of basis according to material and geometric properties of the periodic structure.