Monolithic Additively Manufactured Broadband Horn Array Antenna in $W$ Band

This letter presents the design, fabrication, and experimental validation of a fully metallic$4\,\times \,4$horn array antenna operating in the entire$W$-band ($75-110\,$GHz). The array integrates a broadband$1:16$beamforming network and 16 pyramidal horn elements into a single monolithic structure. The beamforming network is composed of wideband twisters and E-plane power dividers, which are compatible with the metal-only additive manufacturing (AM) technique called laser powder-bed fusion (LPBF). The simulation and measurement results confirm a reflection coefficient below$-12\,$dB in a 37.8% relative bandwidth, with a measured realized gain exceeding$21\,$dBi across the band. The array achieves an aperture efficiency of approximately 80% (calculated usingrealized gain) while maintaining sidelobe levels below$-10\,$dB.