Design of angle-selective surface with narrow angular domain and ultra-narrow angular transition range

This letter presents an angle-selective surface (ASS)with a narrow angular domain and narrow angular transitionrange. The proposed ASS consists of two identical frequency-selective surface layers separated by an air gap. The proposedstructure allows electromagnetic waves to transmit at specific in-cident angles under TE polarization, exhibiting sharp angularselectivity while maintaining a relatively compact unit cell size. At17.74 GHz, it permits transmission for waves incident at 30◦ withan extremely narrow acceptance angle range of 29.95◦ to 30.25◦(S₂₁ > −1 dB), demonstrating high transmission efficiency. Si-multaneously, it effectively blocks waves at incident angles of 0◦ to26◦ and 33◦ to 80◦ (S₂₁ < −20 dB), featuring an ultra-narrowangular transition range that mitigates cochannel interference insignal transmission. Furthermore, an equivalent circuit model wasdeveloped to analyze the structure, and a prototype was fabricatedto validate its performance. The measured results agree well withsimulations, confirming the effectiveness of the proposed design.