Millimeter-wave slotted waveguide array with unequal beamwidths and low sidelobe levels for vehicle radars and communications

A low profile, high gain 32 × 64-slot array antenna with unequal beamwidths in the E- A nd H-planes and low sidelobes is proposed for vehicular applications in the 71-81 GHz band. The antenna is composed of 512 (16 × 32) 2 × 2-slot subarrays arranged with equal spacing and excited by a nonuniform corporate-feed-network. A two dimensional amplitude-tapering (complying with Taylor distribution) is used to achieve the low sidelobe levels (SLLs). Combined with the different dimensions of the array, the sidelobes and the beamwidths in the E- A nd H-planes are independently controlled. A prototype slotted waveguide array is fabricated to verify the array properties. Measurements show that the matching of the array is better than-14 dB over the entire bandwidth. The first SLL is lower than-18.9 dB/-24 dB with the maximum 3-dB beamwidth of 2.3°/1.3° in the E-/H-plane, respectively. The peak gain of over 39.4 dBi and the cross-polarization discrimination (XPD) of below-36.2 dB are also achieved. The demonstrated features of high gain, low SLL, and independent controllability of the beam in the E- A nd H-planes are most desirable for vehicular communications and radars.