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Abstract-Circularly symmetric patch antennas tuned by transversely magnetized lossy ferrite are studied. The circular and ring patch geometries printed on ferrite substrate or tuned by ferrite post and ferrite toroid are studied. Both saturated and partially magnetized ferrite are considered. Strong effects on the dispersive properties of modes propagating under the patch and in turn on the antenna resonant frequency and input impedance are observed when the ferrite losses are taken into account. The patch antennas resonance at a novel mode propagating in the traditionally assumed switch-off frequency range of negative effective permeability constitutes an essential original contribution of this work. In all cases the dynamic control of the patch resonant frequency through the DC-biasing field is investigated. The "perfect magnetic walls approximation" was employed in the analysis since it offers a valuable physical insight as well as simplified closed form expressions for the resonant conditions. These are used as engineering design formulas for an initial antenna design, which is in turn fine tuned with the aid of a numerical simulation-optimization scheme. The validity of the present method was verified through comparisons with published experimental results and numerical simulations.

Abstract-A reconstruction algorithm for two-and three-dimensional microwave imaging is proposed. The present effort is focused on the reconstruction of conductivity (σ) and permittivity (ε r ) distributions aiming at a technique serving medical imaging, while permeability imaging can be easily incorporated to serve geophysical geophysical prospecting as well. This work constitutes the most recent one within the effort of extending our Modified Perturbation Method (MPM) from static to high and now microwave frequencies. MPM is an approximate method based on an exact Sensitivity or Jacobian matrix for an iterative update of an initial (σ, ε r ) guess until convergence. This method is proved almost immune of the problem inherent illposedness, but its robustness is actually gained by paying a penalty of compromised accuracy in the final achieved image. However, this image can be fine tuned by formulating and solving an exact inverse problem. Regarding the involved Jacobian matrix, this is evaluated through closed form expressions obtained through an Adjoint Network Theorem in conjuction with the electromagnetics reciprocity theorem. The field distributions required for its evaluation are readily available from the always required forward problem solutions on the assumed (σ, ε r ) distributions. Herein, the finite element method along with absorbing boundary conditions are employed for the forward problem electromagnetic simulation.

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