Millimeter-Wave Navigational Radar Antenna with Radiating Horn Aperture Fed by a Gap Waveguide

A navigational radar antenna comprising $4\ \mathrm{x}\ 32$ radiating elements fed by a ridge gap waveguide is presented. The antenna is designed at a millimeter-wave frequency band with a grid of horns making the aperture. The proposed structure has no electrical contact between the layers. There are a total of three metal layers, each separated by a small gap. A set of four horns forms an antenna unit cell which is fed by a single cavity-backed slot. The top metal layer is a radiating layer comprising a grid of 32 horn-based unit cells. The E-plane sectoral horn is used as a radiator and is optimized to reduce mutual coupling between adjacent horn elements. A cavity layer is added in the middle to increase the impedance bandwidth of the antenna. The complex distribution network based on the ridge gap waveguide lies at the bottom which feeds the array corporately. Circular Artificial Magnetic Conductor (AMC) pins are designed that confines the input power within the prescribed path. 3dB power dividers are designed with equal amplitudes and phases at all output ports. The proposed antenna array has a relative impedance bandwidth of 13.7 ^% with an input reflection coefficient better than -10dB from the 65 GHz to 65.9 GHz frequency range.