Planar SIW cavity-backed antenna loaded with slots for multiband operations

Abstract

A low-profile substrate integrated waveguide (SIW) cavity-backed antenna loaded with slots is presented for multiband operations. This antenna is designed by loading a rectangular and square-shaped slot onto a rectangular SIW cavity for multiband radiation. The slots are created inside the rectangular cavity to induce a hybrid mode (i.e. ${\text{TE}}_{110} + {\text{TE}}_{120}$), which supports to radiate a lower resonance frequency. The rectangular slot is used to excite ${\text{TE}}_{120}$ mode at 5.21 GHz, while square-shaped slot excites hybrid mode at 2.21 GHz. This hybrid mode is obtained by coupling the cavity modes ${\text{TE}}_{110}$ and ${\text{TE}}_{120}$ through the metallized via-holes. The designed antenna yields multiband response owing to resonant slots when governed by the inset microstrip feedline. The operating modes are explained with the help of mode theory mechanism. The fabricated antenna comprises with dimensions 30 $\times$ 30 $\times$ 1.6 mm³, which is printed on a low-cost Flame Retardant-4 dielectric substrate. To verify the simulated counterparts, the fabricated antenna has been tested, which offers a fractional bandwidth of 6.9% (2.10–2.25 GHz) in the hybrid mode at 2.18 GHz, 8.4% (3.35–3.64 GHz) in the ${\text{TE}}_{110}$ mode at 3.45 GHz and 10.8% (5.04–5.61 GHz) in the ${\text{TE}}_{120}$ mode at 5.26 GHz with suitable far-field pattern.