A Feeding Network with Collinearly Centered Longitudinal Coupling Slots for a Rectangular Parallel-Plate Slot Array Antenna

This paper proposes a novel feeding network with collinearly centered longitudinal coupling slots for uniform excitation of rectangular parallel-plate slot array antennas. Compared to conventional coupling slots arrangement solutions, longitudinal slots along the centerline of the waveguide on the broad wall are employed for minimizing the vibration of field distribution in the parallel plates. Coupling walls are inserted in the waveguide to produce asymmetry for an appropriate excitation of each slot. The arrayed coupling slots are designed by HFSS, manufactured, and tested experimentally. The measured results show a directivity of 37.1dBi and 87.2% aperture efficiency at 9.65GHz with a reflection level less than -16dB. The novel feeding waveguide realizes a significantly 1.2-dB directivity and 21% aperture efficiency enhancement compared to the traditional feed with inclined coupling slots.