Multi-layer frequency selective surface wideband filter with high selectivity operating in L, S, and C bands

Area of Science:

• Electromagnetics and Applied Physics
• Microwave Engineering
• Materials Science

Background:

• Conventional 2D frequency selective surfaces (FSS) often face limitations in achieving both broad bandwidth and sharp roll-off characteristics.
• The demand for compact, high-performance filters in modern communication systems necessitates innovative designs with improved selectivity and out-of-band attenuation.
• Existing FSS designs may present manufacturing complexities or compromises in performance trade-offs.

Purpose of the Study:

• To design and analyze a novel 2D multilayer FSS passband filter with broadband response and pronounced roll-off.
• To enhance filter selectivity and bandwidth compared to conventional 2D structures while maintaining ease of manufacturing.
• To achieve desired filtering behavior across the L, S, and C communication bands.

Main Methods:

• A layer-by-layer equivalent circuit extraction technique was employed for accurate impedance tailoring.
• A 3-layer stacked FSS structure separated by foam gaps was designed, resulting in a compact 67 mm thickness.
• Analytical modeling was validated through full-wave simulations and experimental measurements.

Main Results:

• The proposed FSS filter exhibits an extensive -3 dB passband from 2.79 GHz to 6.65 GHz, achieving 90% fractional bandwidth.
• Sharp roll-off characteristics of 42 dB/GHz and 70 dB/GHz were achieved.
• The filter demonstrates -10 dB rejection bands covering 1.2-2.62 GHz and 6.75-7.9 GHz, ensuring full L, S, and C band coverage.

Conclusions:

• The novel multilayer FSS design successfully achieves broadband operation with excellent selectivity and sharp roll-offs.
• The filter's compact, lightweight, and affordable nature makes it highly suitable for advanced communication systems.
• The validated performance confirms the effectiveness of the proposed design for applications requiring robust out-of-band signal rejection.