Soğurucu frekans seçici yüzey tasarımı

Abstract

In this study, 11 GHz centered absorptive frequency selective surface is designed with wide transmission band, and wide absorption band at lower frequency spectrum. Designed absorptive frequency selective surface has dual polarization operation capability. Unit element resonators of absorptive frequency selective surface are proposed in order to provide wideband and dual polarization operation, after analyzing possible alternative forms. Novel octagon shaped structure is proposed for resistive layer resonator; and three layered octagon shaped patch-slot-patch structure is proposed for bandpass layer resonator. In literature, unit element resonators of absorptive frequency selective surfaces are synthesized after successive iterations of guess, analysis and update processes. In this study an alternative method is proposed, and unit element resonator of resistive layer is synthesized by genetic algorithm code. During synthesis process, genetic algorithm code controls that synthesized resonator provides targeted frequency response performance and geometry of synthesis is realizable. Synthesis performance of genetic algorithm code is tested for alternative algorithm methods, and capability of proposed resonator is tested for different frequency response performance targets. Designed absorptive frequency selective surface response is analyzed by electromagnetic analysis for horizontal and vertical polarization cases, and for normal and oblique incidence. For normal incidence, surface current and electric field distribution of resistive layer and bandpass layers are investigated. Electromagnetic analysis response of designed absorptive frequency selective surface has 3.47 GHz 1-dB bandwidth which is 32% compared to center frequency. 1-dB cutoff frequencies are 9.63 GHz and 13.10 GHz. It has 4.43 GHz 3-dB bandwidth which is 40% compared to center frequency. 3-dB cutoff frequencies are 9.02 GHz and 13.45 GHz. Lowest insertion loss in transmission band is 0.66 dB. Absorptive frequency selective surface is manufactured as 1x2 unit layers; and measured using WR-90 waveguide test setup for X-band spectrum. Measured frequency response has 3.17 GHz 1-dB bandwidth which is 29% compared to center frequency. 1-dB cutoff frequencies are 9.38 GHz and 12.55 GHz. 3-dB bandwidth is 3.74 GHz which is 34% compared to center frequency. 3-dB cutoff frequencies are 9.14 GHz and 12.88 GHz. Lowest insertion loss measured in transmission band is 0.65 dB.