Ferreira, DavidCaldeirinha, RafaelCuinas, InigoFernandes, Telmo, Telmo Rui Carvalhinho Cunha, Telmo R.2025-06-162025-06-162015Ferreira, David & Caldeirinha, Rafael & Cuiñas, Iñigo & Fernandes, Telmo. (2015). Square Loop and Slot Frequency Selective Surfaces Study for Equivalent Circuit Model Optimization. IEEE Transactions on Antennas and Propagation. PP. 1-9. 10.1109/TAP.2015.2444420.0018-926X1558-2221http://hdl.handle.net/10400.8/13244Published in: IEEE Transactions on Antennas and Propagation ( Volume: 63, Issue: 9, September 2015).Acknowledgment The authors are grateful to Instituto de Telecomunicações Leiria, Portugal, to Polytechnic Institute of Leiria, School of Technology and Management, Portugal, and to Universidade de Vigo, Spain, for making available their facilities used in this research project. This research was partially supported by the Portuguese Government, Portuguese Foundation for Science and Technology, FCT, through the financial support provided under the QREN-POPH funding; and by the Spanish Government, Ministerio de Economía y Competitividad, Secretaría de Estado de Investigacion, Desarrollo e Innovacíon, (project TEC2011-28789-C02-02), AtlantTIC Research Center and the European Regional Development Fund (ERDF).This paper presents a parametric study of square loop and square slot frequency selective surfaces (FSSs) aimed at their equivalent circuit (EC) model optimization. Consideration was given to their physical attributes, i.e., the unit cell dimensions and spacing, substrate thickness and dielectric properties, for several frequencies and plane wave incident angles. Correlation analysis and evaluation of the influence of physical related input parameters on the FSS performance are presented. Subsequent optimization factor for the square loop classical EC model is analyzed, and a novel EC model formulation for the square slot FSS is proposed. The performance of the proposed EC model was assessed against results obtained from appropriate electromagnetic (EM) simulations, based on a root-mean-square error (RMSE) criteria. Results demonstrate the validity of the optimized EC model, in which good estimations of the frequency response of FSS structures were obtained. Significant reduction of the resonant frequency offsets, in the order of 650 (from 910 to 260) and 460 (770 to 310) MHz, was obtained for square loops and square slots, respectively. The models were further validated against measurements performed on two physical FSS prototypes inside an anechoic chamber at 2.4 GHz. Relatively good agreement was obtained between measurements of real FSS prototypes and results obtained with the EC model. Finally, this work is sought to provide the necessary refinement of elementary models for further studies with more complex and novel FSS structures.engFrequency selective surfaces (FSS)equivalent circuitsindoor radio communicationradio propagationsimulationmeasurementjournal article10.1109/tap.2015.2444420