A Metasurface-based Bandpass Filter in Ka-Band for Space Applications

In this paper, a multi-layered metasurface (MS) structure has been proposed as Ka-band filter having extremely low insertion loss and sharproll-off characteristics towards space application. Three identical distinct layers of RT Duroid 6010 substrate have been used in which the proposed structure has been designed. The unit cell of the structure consists of a square metallic slot together with a square metallic ring slot in the top and bottom surfaces of the middle layer of RT Duroid 6010 substrate. The proposed design offers bandpass characteristics over 27.5 GHz to 30.5 GHz combined with a sharp rejection of $4 \mathrm{~dB} / \mathrm{GHz}$ out-of-band. The proposed filter offers $0.3 \mathrm{~dB}, 1 \mathrm{~dB}$ and 3 dB bandwidths of $2.08 \mathrm{GHz}, 3.17 \mathrm{GHz}$ and 4.36 GHz respectively. The extremely low insertion loss lesser than 0.4 dB has been achieved in the passband. The structure offers angular stability up to $\mathbf{3 0}^{\circ}$ along with polarization independent feature. Being compact in nature, the structure is suitable for space applications.