SLM Printed Millimeter-Wave Multibeam Antenna Array Based on Filtering Butler Matrix

In this communication, a 3-D-printed filtering Butler matrix-based <tex-math notation="LaTeX">1×4 </tex-math> multibeam antenna array is investigated in the Ka-band. The Butler matrix consists of all-resonator 180° filtering hybrids, 90° couplers, and phase shifters, providing incremental phase gradients along with a bandpass characteristic. Four wideband horns are employed as the radiator array. The proposed design eliminates the requirement of crossovers and connectors between the Butler matrix and radiators, resulting in a much compact structure. The <tex-math notation="LaTeX">1×4 </tex-math> multibeam filtering antenna array prototype is monolithically fabricated using selective laser melting (SLM) 3-D printing technology. The prototype achieves an impedance bandwidth (return loss > 10 dB) of 28.1–29.8 GHz, a gain of up to 16.2 dBi, and stable radiation beams at 0°, ±23°, and ±46°. Meanwhile, beyond the operating bandwidth, the realized gain experiences a suppression of more than 30 dB. The proposed filtering Butler matrix-fed multibeam array, characterized by its high efficiency, large power capacity, and excellent frequency selectivity performance, demonstrates potential applications in millimeter-wave (mm-Wave) communication systems.