A beam switching slot array with a 4-way Butler matrix installed in a single layer post-wall waveguide

The authors propose a switched beam slot array antenna with the 4-way Butler matrix. All are integrated in one substrate. Experiments in the 26 GHz hand confirm the key operation of this structure of the antenna; four almost-identical beams are switched to cover the total horizontal 90-degree sector with equal angular spacing. A gain of 21.3 dB was observed though two beams have a lower gain by about 1.8 dB due to the grating lobes. A narrower waveguide could eliminate the defects.