A 3-D-Printed High-Gain Double-Ridge Waveguide-Fed Parallel-Plate Horn Array for 5G Millimeter-Wave All-Band Applications

A novel three-dimensional (3D) printed double-ridge waveguide fed parallel-plate horn antenna array is presented for the fifth-generation (5G) millimeter-wave all-band coverage. By loading hourglass shaped ridges into the proposed horn radiators and metallic baffles at the ends of linear horn arrays, the quasi-TEM mode is excited over the radiation aperture throughout a wide bandwidth. Air slits are added between H-plane linear arrays to reduce the grating lobe level of the array. By the two means, an enhanced bandwidth with stable high-gain radiation is obtained by the proposed array without need of reducing element spacing. A theoretical analysis reveals that benefitting from a lower rate of change for the propagation constant of the used double-ridge waveguides, the frequency points where in-phase superposition of small reflections existing in full-corporate feed networks occurs shift towards higher frequencies. The intervals between adjacent frequency points with strong reflections are also enlarged. As a result, the number of undesirable strong-reflection points decreases in the target frequency range such that a superior bandwidth is obtained by the proposed large-scale array without increasing design complexity. A 16 × 16 array prototype with dimensions of 146 × 134 × 31.8 mm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> experimentally confirms excellent performance, including a bandwidth of 60% from 23.8 to 44 GHz, a gain of up to 34.7 dBi and stable radiation patterns, which is valuable to wideband backhaul and wireless access applications in 5G and beyond 5G (B5G).