A Wideband Substrate Integrated Waveguide Slotted Array Antenna with Multimode and Multidirectional Characteristics

This paper presents the design of a substrate integrated waveguide slotted array antenna (SIW-SAA) with wideband, multimode and multidirectional characteristics. The slotted array consists of three transverse slots in the top wall of SIW which are inclined at 45 degrees with respect to a single longitudinal slot. The number of slots and the position of the slotted array determine the impedance bandwidth. It is found from the simulated and measured results that the impedance bandwidth of the antenna is 92% (10 GHz - 27 GHz) for S11 <= - 10 dB. Multiple modes get excited in the SIW-SAA resulting in multidirectional characteristics and an equivalent circuit model is used to explain the physics of this phenomenon. In the X band, the lowest mode (TE10) of SIW exists and the combination of slotted array and SIW is responsible for unidirectional radiation. Bidirectional and omnidirectional patterns are observed in the elevation plane for Ku and K bands, respectively due to higher order modes that are excited in the bottom wall of SIW. With these multidirectional characteristics, the proposed antenna is an attractive choice in airborne control systems, long distance communications and broadcasting.