Within a context of commercialization of 5G communication technology and rapid development of satellite communication and technological innovation, this paper presents a three-band binary MIMO antenna based on an “X”-shaped isolation structure. The antenna consists of two inverted, parallel unit radiating patches, with isolation enhanced by loading isolation branches on both the front and back sides. A slotting technique was applied on the back of the antenna to improve bandwidth. The overall dimensions of the antenna are 37 mm×25 mm×0.8 mm, and its measured operating bands are 4.3-5.8 GHz, 8.02-9.3 GHz, and 12.2-14.8 GHz. The port isolation exceeds 23 dB within the operating range, while the full-band envelope correlation coefficient (ECC) remains below 0.03, and the diversity gain (DG) exceeds 9.99 dB, indicating excellent diversity performance. These results demonstrate that the antenna meets MIMO-antenna transmission performance requirements and is well-suited for 5G and satellite communication systems.