Wideband arrays have recently received considerable attention in 5G applications to cover larger frequency bands. This paper presents a novel design of a high gain and wideband antenna subarray from 23 GHz to 32 GHz, which covers the frequency bands proposed by the Federal Communications Commission (FCC) for 5G communications. The proposed subarray consists of four radiating elements with wideband and high gain characteristics. These elements are composed of two stacked patches, which are fed using the proximity coupling technique. A unit-cell element prototype is first fabricated and tested to validate the gain and bandwidth performances. A 1x4 subarray prototype is then fabricated and tested, while maintaining an element spacing less than half-wavelength at the center frequency, to avoid grating lobes and to keep the small size of the antenna subarray. The measurement results of the prototypes, i.e. unit cell element and subarray prototypes, show good agreements with the simulations. The subarray measurements demonstrate a high gain of 10-12 dBi, an impedance bandwidth of 33.4 %, and a 1-dB gain bandwidth of 10.5 %. The proposed antenna subarray is a good candidate for wideband and high gain antenna arrays suitable for 5G mmW applications.
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