Multibeam Array Antenna with Compact Size Butler Matrix for Millimeter-Wave Application

New radio wave technologies of millimeter-wave (mmWave), compact cell size, and multi beam base station are introduced with the recent development 5G mobile system. The Butler Matrix (BM) feed circuit is most preferable candidate for system since it can achieve radiationpatterns at array antenna, provide structural compactness produce good beams.The BM typically built on a single dielectric substrate. However, in this single-substrate structure, micro strip line connecting several elements spans over large area, resulting significant feeding loss millimeter frequency band.In study, size configuration proposed, where original structure modified into two-substrate stacking structure. via-hole designed to connect two substrates minimal path loss. 28 GHz band four inputs outputs.The phase delay optimized using difference ±45º ±135º. coupling hybrid -3 dB, while transmission coefficient -6 ± 3 achieved from and, return (Sii) both input output ports less than -10 dB. combined rectangular patch antenna planar 0.5 λ0spacing obtain radiation patterns. When Port 1 through 4 fed, beams created, peak gains 11.2 dBi, 9.87 10.2 11.7 respectively, towards +16°, -35°, +39°, -12°. analysis includes performance ideal value input. Three-dimensional representations multibeam patterns obtained after each signal fed