Horizontally polarized low sidelobe level inclined-slot array antenna using ridged waveguide

Abstract In this paper, based on a ridge waveguide, an inclined-slot array antenna possessing horizontal polarization and low sidelobe level is designed and fabricated. The slot array is modeled by a circuit consisting of a series of impedances. Then the impedances are determined such that the desired aperture distribution is achieved. The resultant impedances are then synthesized by appropriate inclined slots. Through this design, a horizontal polarization antenna with a low level of sidelobes (−25 dB) is achieved while the dimensions of the antenna are decreased due to using the ridge inside the waveguide. The antenna is fabricated and measured. Apart from a good agreement between the simulation and measured results, the antenna possesses a stable gain of approximately 14.5 dBi at the entire frequency band. Further, the sidelobe level is −24.9 dB and the reflection coefficient is below −20dB at the center frequency, making the antenna a good choice for radar applications where a low level of ground clutter is desired.