This paper describes the design and implementation of an all-metal wideband cavity-backed slot array antenna specifically optimized for 5G sub-6 GHz networks. The antenna is engineered to feature low sidelobe levels (SLL), which enhance signal clarity and reduce interference. The proposed antenna utilizes a novel approach, directly exciting all radiating slots through the cavity layer, thus eliminating the need for a complex and lossy power dividing network. The antenna's performance is validated through full-wave simulations and measurements. The results demonstrate antenna's ability to achieve wideband operation from 3.1 to 4 GHz with - 19 dB SLL, peak gain of 20.2 dBi, and more than 90% total efficiency. The main advantages provided by the proposed slot arrays are wide bandwidth, high radiation efficiency, high gain, low sidelobe levels. The all-metal construction ensures robust power handling, and the simplified design contributes to its low complexity. These characteristics make the antenna a promising candidate for 5G deployments.