Dual-band bandpass transmissive metasurface based on a high-permittivity dielectric substrate with polarization and angle robustness

Transmissive metasurfaces, as a common type of electromagnetic metasurfaces, play a significant role in regulating incident electromagnetic waves in the frequency domain. However, most previously reported transmissive metasurfaces have only a single transmission band, and even the few with two transmission bands cannot simultaneously achieve both wide-angle transmission within the transmission band and out-of-band suppression between the two transmission bands across different incident angles. To address this limitation, we propose a dual-band bandpass transmissive electromagnetic metasurface that can operate simultaneously in the Ku and Ka bands with out-of-band suppression between the two transmission bands under dual-polarized incident angles from 0^◦ to 80^◦, which has the potential to be applied to improve the anti-interference capability of frequency-division duplexing technology and enable full utilization of millimeter-wave spectrum resources. Our proposed metasurface contains two identical honeycomb patterns printed on both sides of a dielectric substrate with a relative permittivity of 20. Compared with common substrates, this substrate has a relatively higher permittivity, which can further reduce the unit cell size of periodic structures and thereby reduce the impact of higher-order mode effects on structural performance. Within the frequency band from 5 to 40 GHz, our proposed metasurface can generate two bandpass transmission peaks around 16.3 and 34.1 GHz for dual polarizations with incident angles from 0^◦ to 80^◦. For substrates with lower permittivity, the bandpass transmission characteristic at high frequencies cannot be obtained due to higher-order mode effects. An equivalent transmission line circuit model of this metasurface is proposed to predict and analyze the simulated transmission performance at the two transmission peaks across different incident angles. The prototype has been fabricated and measured. Measured results are in good agreement with simulated results.