A novel design approach for FSR structures realizing dual absorption bands and dual transmission passbands

The absorption–transmission–absorption–transmission (A-T-A-T) type Frequency Selective Rasorber (FSR), featuring dual absorption bands and dual transmission passbands, has attracted considerable attention for modern electromagnetic applications. However, most existing A-T-A-T FSR designs cannot simultaneously achieve a wide absorption bandwidth and low insertion loss, which limits their practical use in high-performance systems. To overcome this challenge, a polarization-insensitive and miniaturized A-T-A-T type FSR with wide absorption bandwidth and low insertion loss is proposed. The lossy layer consists of metallic patterns loaded with four resistors, which broadens the lower-frequency absorption band. The lossless layer is designed as a bandpass frequency selective surface incorporating a cross-shaped slot and four rectangular apertures, generating two transmission poles for dual-band transmission. The proposed structure operates over 3.59–18.6 GHz (135.29%), exhibiting two absorption bands of 3.59–13.7 GHz (116.95%) and 16.21–17.13 GHz (5.52%). In addition, two transmission passbands are obtained at 15.05 GHz and 18.6 GHz, with minimum insertion losses of 0.59 dB and 0.58 dB, respectively. Furthermore, the proposed design provides polarization insensitivity, stable performance under oblique incidence up to 45°, and compact dimensions with a thickness of 0.078 λ and a unit-cell size of 0.014 λ 2 . To verify its practical feasibility, a 20 * 20 array prototype was fabricated and measured. The measured results agree well with the simulated ones, confirming the effectiveness and reliability of the proposed design. Owing to its balanced and comprehensive performance, the proposed A-T-A-T type FSR is a promising candidate for dual-band radiating system shielding, radar cross-section (RCS) reduction, and electromagnetic interference (EMI) suppression.