LAUSR

3-D printed air-filled waveguide fed horn antenna arrays are investigated in the Ka-band. Pyramidal E-plane horn antennas with a small size are introduced as the radiating element to improve the bandwidth and radiation characteristics of the array. Commercial direct metal laser sintering technology is applied to print the antenna structure in a whole piece. Excellent operating performance including wide impedance bandwidths of 25.8% and 23.8% for $\vert \text{S}_{11}\vert < -10$ dB, gains up to 27.5 and 33.8 dBi with a variation of less than 1.5 dB over the operating band and radiation efficiencies of around 90% and 80% is obtained experimentally by two fabricated prototypes consisting of 64 and 256 radiating elements, respectively. Stable radiation patterns with low cross polarization are confirmed as well. The array designs and results obtained in this paper verify the feasibility of utilizing advanced a 3-D printing technique to realize millimeter-wave large-size antenna arrays with complicated multilayered configurations, which is of value for various wideband millimeter-wave wireless applications.