A Wideband Slotted Spherical Waveguide Antenna Based on Multi-Mode Concept

A wideband slotted spherical waveguide antenna based on the multi-mode concept is presented. The proposed design starts from a metallized spherical cavity fed by a rectangular waveguide. Then, two groups of slots are symmetrically cut on the shell. By suitably choosing the slot dimensions and locations, four radiation modes can be excited in a single radiator and merged with each other, resulting in a wideband radiation characteristic. To verify this, a prototype is designed and fabricated using stereolithography apparatus to achieve a light weight. As the measured fractional bandwidth (FBW) of the proposed antenna can be increased to 70.1% while maintaining stable radiation patterns and high gain, a simple and effective design of wideband slotted waveguide antennas with good radiation characteristics can be validated.