Low-Profile Circular Patch Array Fed by Slotted Substrate Integrated Waveguide

A linear array antenna comprising circular-shaped patches fed by slotted substrate integrated waveguide is proposed. The slotted circular-shaped patch operates at the quasi-TM21 mode, which produces boresight radiation with an improved gain due to the introduction of additional slot loadings in the middle space of the circular-shaped patch. Comparisons among the proposed 1 × 8 linear array antenna and two other traditional linear arrays used in automotive radars are presented, highlighting the superior performance of the proposed linear array, i.e., higher gain and wider 1 dB gain bandwidth. Several key geometrical design parameters, which are critical to the performance of the array antenna, are studied and analyzed to provide a better understanding of the proposed array antenna. A 4 × 8 planar array antenna incorporating four 1 × 8 linear arrays is further designed to verify the extension capability of the proposed linear array. Both the linear array and the planar array antennas were fabricated and measured, showing a good agreement between simulation and measured results, thus validating the designs. The proposed array antenna can be a good candidate for millimeter-wave automotive radar applications.