# The Effect of the Equivalent Permittivity Model in Contactless MIMO-GPR Imaging

## TL;DR

This paper introduces a new imaging method for ground-penetrating radar that improves accuracy and efficiency in detecting subsurface objects.

## Contribution

A novel contactless MIMO-GPR imaging approach using equivalent permittivity and adjoint inversion is proposed.

## Key findings

- The proposed method achieves reliable subsurface target reconstruction.
- Numerical simulations confirm the method's accuracy and computational efficiency.

## Abstract

Multiple-Input–Multiple-Output Ground-Penetrating Radar (MIMO-GPR), collecting multiview–multistatic data, is now becoming an assessed diagnostic tool, enabling enhanced reconstruction accuracy and subsurface target detection due to the exploitation of multiple Tx/Rx channels. In this context, the present work deals with a 2D radar imaging approach for contactless MIMO GPR based on the equivalent permittivity concept. The imaging problem is formulated as a linearized inverse scattering problem under Born approximation, and a ray propagation model, based on equivalent permittivity spatially varying along depth, is adopted to account for the wave propagation through the air–soil interface. The resulting linear inverse problem is solved by means of an adjoint inversion, enabling reliable target reconstruction. Despite the approximation introduced by the present formulation, numerical simulations show that the proposed imaging strategy is sufficiently accurate from an engineering viewpoint and is computationally efficient.