A Compact and Simply-Constructed All-Metal Circularly Polarized Ridge-Waveguide Slotted Antenna Array for Vehicle Mounted Satcom on the Move (SOTM) Communication Application

In this paper, a novel circularly polarized (CP) ridge-waveguide slotted antenna array is proposed for vehicle used Satcom on the Move (SOTM) applications. The antenna array is designed closely following the required factors for generating the circular polarization. The proposed antenna array is constructed on a symmetrical single-ridge slotted waveguide. Each antenna element consists of a pair of inclined slots opened on the narrow walls, and longitudinal slots opened on the bottom of the U-shaped wall of the waveguide. The inclined slots and the longitudinal slots are able to radiate orthogonal electric-fields independently with a phase-difference of 90°. After a vector superposition in the far-field by using this design, the circular polarization could be realized with extremely low axial ratio theoretically. Several essential parameters affecting the CP performance are also studied in this paper. To verify the feasibility of the proposed approach, a four-element CP antenna array is simulated, fabricated and measured. Results show that the obtained prototype achieves a measured impedance bandwidth of 14.74% from 9.24 GHz to 10.71 GHz with S11 <−10 dB, and a 3-dB axial ratio bandwidth of 19.1% from 9.0 GHz to 10.9 GHz.