Aperture coupled feeding patch (ACFP) Array antenna Millimeter-wave Wide bandwidth Millimeter-wave (mmW) antenna is one of the most important parts of the fifth-generation (5G) systems because of its advanced characteristics, for example, wideband and high transmission rate. In this paper, an mmW 4x1 array antenna with high gain and wideband based on an aperture coupled feeding patch (ACFP) antenna is presented. The proposed array antenna operates at 28-GHz frequency. The antenna has a wide operating bandwidth of around 12.6 % at-10 dB bandwidth that covers 26.65 GHz to 30.35 GHz. The peak gain of the array antenna is approximately 13 dBi at 28 GHz and kept maintained in all interested frequency band. The proposed antenna is designed using a 0.127-mm thick Duroid 5880 substrate with a compact substrate of dimensions of 25 mm x 48 mm x 0.754 mm.