A Novel SIW Cavity-Backed Multiband mm-Wave Antenna for 5G (n257/n260), K-Band, and Q-Band Applications

A compact, single-fed low-profile substrate-integrated waveguide (SIW) cavity-backed multiband slot antenna (CBMSA) with a simplified feeding structure is proposed for millimeter-wave (mm-wave) applications. Designed on a single-layer substrate, the antenna achieves multiband operation with high radiation efficiency by employing a circular SIW-backed cavity incorporating four radiating slots—two long and two square-shaped strips—etched from the cavity to enable efficient radiation at higher-order resonances. The proposed antenna resonates at eight distinct frequency bands: f<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</inf> = 25.77 GHz, f<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> = 27.15 GHz, f<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> = 29.31 GHz, f<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</inf> = 31.10 GHz, f<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</inf> = 32.84 GHz, f<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</inf> = 34.61 GHz, f<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">7</inf> = 36.03 GHz, and f<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">8</inf> = 37.39 GHz, with corresponding impedance bandwidths of (25.63–25.92 GHz), (26.78–27.52 GHz), (28.90–29.75 GHz), (30.76–31.40 GHz), (32.53–33.39 GHz), (34.06–35 GHz), (35.98–36 GHz), and (37.17–37.62 GHz). This design effectively covers multiple mm-wave frequency bands, including the K-band, Q-band, 5G n257, and 5G n260, making it highly suitable for 5G communications, satellite links, and high-frequency radar applications. The antenna demonstrates excellent impedance matching, satisfactory gain performance, and high radiation efficiency, making it a promising candidate for next-generation wireless communication systems.