To address the broadband coverage challenges in the mid-band of 5G in China and to enable future applications of 6G systems in the sub-7 GHz frequency range, this paper presents the design of a coplanar waveguide (CPW)-fed ultra-wideband, high-isolation multiple-input multiple-output (MIMO) antenna that covers the 5G frequency bands. The antenna element is based on a single elliptical patch, and ultra-wideband performance is achieved by incorporating a trident-shaped structure and cornercutting techniques. The antenna consists of two slot antenna elements, suitable for a 2×2 MIMO antenna array configuration, with overall dimensions of 118×66×0.8 mm. The two antenna elements are arranged in a parallel configuration, with their ground planes interconnected. Additionally, an “H”-shaped fence structure is introduced between the elements to improve isolation. Experimental results showed that the antenna can operate across a bandwidth of 1.15-7.80 GHz, with isolation greater than 20 dB across the operating band. The envelope correlation coefficient (ECC) was below 0.03, and the diversity gain (DG) exceeded 9.98 dB. The designed MIMO antenna features high isolation and ultra-wideband coverage, and the CPW feeding structure facilitates its integration into integrated circuits and various ultra-wideband systems. This antenna showed promising application potential in both current 5G and future 6G systems.