Volume reduction of planar substrate integrated waveguide cavity-backed antennas

A technique to reduce the volume of a planar substrate integrated waveguide (SIW) cavity-backed antenna is presented. The volume reduction is accomplished by incorporating a capacitive element with the purpose of reducing the resonant frequency of the cavity. The paper presents the cavity design process, the external coupling used to feed the cavity, the antenna layout and, finally, the procedure employed to modify the operational frequency of the system, accomplishing the volume reduction. The designed compact cavity-backed antenna was manufactured and measured, obtaining: central frequency (f₀) of 3.67GHz, -10dB fractional bandwidth (FBW) of 0.7%, gain (G) of 4.46dBi and, front-to-back ratio (FTBR) of 14dB in the direction of maximum radiation.