Permittivity of the dielectric objects is calculated using the scattered fields from objects and the incident fields in the investigation domain. In practical applications, calculation of incident fields over closely placed discrete points is a challenging task. In this study, a simple method to calculate incident fields using equivalent sources is proposed. These equivalent sources are modelled from the measured incident fields around the dielectric objects. From these sources, permittivity of the dielectric objects is calculated on experimental data set by employing contrast source inversion technique. Further, the accuracy of the proposed method is studied on synthetic data by approximating the pyramidal horn antenna fields with line and equivalent sources.

In this paper, a regularized reconstruction based on the minimal residual method is proposed for microwave imaging applications. The method provides optimum regularization parameter to estimate the distribution of permittivity values of unknown scatterers under test. Initially, the method is applied to Born approximated linear model for weak scatterers. The performance of this approach is compared with the commonly adopted Morozov's discrepancy principle used in conjunction with the Tikhonov regularization. The effectiveness of the method is assisted by simulating the various numerical examples of synthetic and experimental data. The results of numerical simulations validate that the proposed method is highly effective. Thereafter, a non‐linear inverse problem based on the inexact Newton method is examined for the estimation of strong scatterers. Here also, the proposed method is found to be helpful in terms of improving the image accuracy.

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