# Inversion of Multi-frequency Data with the Cross-Correlated Contrast Source Inversion Method

## TL;DR

This paper introduces a multi-frequency extension of the cross-correlated contrast source inversion (CC-CSI) method for electromagnetic inverse scattering, demonstrating improved performance over existing methods through numerical and experimental results.

## Contribution

The paper proposes a novel multi-frequency CC-CSI method that enhances inversion accuracy for complex scatterers using electromagnetic data.

## Key findings

- Multi-frequency CC-CSI outperforms MR-CSI in complex scatterer inversion.
- Numerical and experimental results validate the effectiveness of the proposed method.
- The method is applicable to both TM and TE polarizations.

## Abstract

Cross-correlated contrast source inversion (CC-CSI) is a non-linear iterative inversion method that is proposed recently for solving the inverse scattering problems. In CC-CSI, a cross-correlated error is constructed and introduced to the cost functional, which improves the inversion ability when compared to the classical design of the cost functional by exploiting the mismatch between the data error and state error. In this paper, the multi-frequency inversion for electromagnetic waves is considered and a multi-frequency version of CC-CSI is proposed. Numerical and experimental inversion results of both transverse magnetic (TM) and transverse electric (TE) polarization demonstrate that, when multi-frequency data are available, CC-CSI still outperforms the multiplicative-regularized CSI method (MR-CSI) in the inversion of more complicated scatterers.