Abstract
A bandwidth enhancement method has been described in this paper by using the various cavity modes. The cavity is achieved by a wisely developed substrate integrated waveguide (SIW) technology, which realizes a non-planar cavity-backed antenna in planar form. The whole antenna circuit and feed are integrated on the same plane. Rather than using a conventional slot, a dual T-shaped slot is preferred as a radiating element. The combination of dual T-shaped slot and a shorting via enhances the bandwidth. The slot yields three resonances due to TE110 mode and modified TE120/TE130 modes. The placement of shorting via modifies TE110 mode, which gets coupled with the other higher-order modes and enhances the bandwidth by 50%. The footprint of the square SIW cavity of antenna is 0.86 lambda(g) x 0.86 lambda(g) mm(2). The proposed geometry is prototyped and experimentally tested. The antenna covers a bandwidth of 400 MHz (6.75-7.15 GHz) with gain of 5.5-6.1 dBi. The antenna shows a front-to-back ratio better than 15 dB with a unidirectional radiation pattern and the cross-polar level below - 15 dB. The antenna is fabricated on a thin substrate of profile 0.052 lambda(g) on a single layer. In addition, the proposed structure possesses the advantages of low profile, planar, compact size with flat gain and uniform radiation features.