Application of MUSIC-type imaging for anomaly detection without background information

TL;DR

This paper analyzes the limitations of the MUSIC algorithm in microwave imaging when background parameters are unknown, deriving an analytical expression and showing that anomaly detection depends on permittivity and conductivity values.

Contribution

It provides the first analytical expression of the MUSIC imaging function without complete background information and clarifies how background parameters affect anomaly localization.

Findings

Anomaly detection is sensitive to permittivity and conductivity values.

Small conductivity values allow anomaly recognition despite unknown background.

Analytical expression involving Bessel functions explains MUSIC failure modes.

Abstract

It has been demonstrated that the MUltiple SIgnal Classification (MUSIC) algorithm is fast, stable, and effective for localizing small anomalies in microwave imaging. For the successful application of MUSIC, exact values of permittivity, conductivity, and permeability of the background must be known. If one of these values is unknown, it will fail to identify the location of an anomaly. However, to the best of our knowledge, no explanation of this failure has been provided yet. In this paper, we consider the application of MUSIC to the localization of a small anomaly from scattering parameter data when complete information of the background is not available. Thanks to the framework of the integral equation formulation for the scattering parameter data, an analytical expression of the MUSIC-type imaging function in terms of the infinite series of Bessel functions of integer order is derived. Based on the theoretical result, we confirm that the identification of a small anomaly is significantly affected by the applied values of permittivity and conductivity. However, fortunately, it is possible to recognize the anomaly if the applied value of conductivity is small. Simulation results with synthetic data are reported to demonstrate the theoretical result.