Polarization-Independent Metasurface Based Bandpass Filter in Ka-Band With High Roll-Off

This paper presents a multi-layered metasurface (MS) structure as a Ka-band filter with extremely low insertion loss and sharp roll-off characteristics for space application. Three identical layers of RT Duroid 6010 substrate have been used to design the proposed structure. The unit cell of the structure consists of 2 layers of metal with a square metallic slot along with a square metallic ring slot. In addition to that, the top metal layer comprises additional slot at the edges along with a metallic strip at the center of the edge. These two metal layers have been sandwiched between 3 layers of identical RT Duroid 6010 substrate. The proposed design offers bandpass characteristics over 27.5 GHz to 29.5 GHz combined with a sharp out-of-band rejection of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$18 ~\text{dB} / \text{GHz}$</tex>. The proposed filter offers <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$0.3 ~\text{dB}, 1 ~\text{dB}$</tex>, and 3 dB bandwidths of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$1.9 \text{GHz}, 2.47 \text{GHz}$</tex>, and 3.31 GHz respectively. The extremely low insertion loss of less than 0.4 dB has been achieved in the passband. The structure offers angular stability up to 30° along with polarization-independent feature. Being compact in nature, the structure is suitable for space applications.