A Low Sidelobe Waveguide Slot Antenna with Loading Patches Array

In this paper, we propose a low sidelobe waveguide slot antenna with loading patches array. We use SIW structure at the bottom of the antenna to form a rectangular waveguide cavity, etch eight equally sized gaps above it, and load patches array at the top of antenna. Eight different sized patches are used to achieve a low sidelobe design. The simulation results indicate that the antenna maintains a low sidelobe level, below -19.6 dB, across the frequency range from 76 GHz to 77.25 GHz, and boasts a broad operational bandwidth extending from 76 GHz to 80.5 GHz. a high gain of 13.85 dBi and a high radiation efficiency of 96.3% at 77 GHz.

I. Introduction

Slot antennas utilizing rectangular waveguides with Substrate Integrated Waveguide (SIW) technology have been the focus of extensive research. They are renowned for their compact design, minimal losses, high gain, and high radiation efficiency, making them highly suitable for integration into microwave and millimeter-wave circuits. Typically, a uniform arrangement of SIW slot antennas yields a sidelobe level (SLL) around -13.6 dB. Nevertheless, there is a general demand for SLL to be lower than -13.6 dB. Consequently, it becomes necessary to implement a technique for reducing the SLL in the slot array. Designing antenna array is a common approach to achieve higher gain and lower SLL. For example, arranging multiple designed antenna units horizontally and using power dividers for feeding [1]–[5]. Additionally, although some waveguide slot antennas based on SIW have low SLL, their working bandwidth are narrow [6]–[7]. For a single antenna unit, the main method to improve low sidelobe performance and working bandwidth include changing the feeding method and designing a new slot array.