In this paper, we propose an enhancement of the Equivalent Circuit Method (ECM) for analysis of frequency selective surface (FSS) with square loop geometry of the unit cell. For this, genetic algorithms and rational algebraic models are used to obtain a more accurate value of the effective electrical permittivity (εeff). We use simulated data obtained with a commercial software to adjust some parameters. So, genetic algorithm is used to obtain a better value of an exponent that calculates εeff minimizing the rational algebraic models. In this paper, this is done for the square loop geometry, but the methodology can be extended to any geometry. Finally, prototypes are built and the technique is validated.
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