In this paper, a MIMO antenna system was designed using two antennas operating in different modes: a ground-radiating antenna based on a half-wavelength structure and a dipole antenna based on a one-wavelength configuration. Due to the distinct operating modes of the two antennas, intrinsic decoupling between the elements is achieved without the need for additional isolation structures. The measured impedance bandwidths of the designed MIMO antenna are 310 MHz and 450 MHz for each element, respectively. The isolation between the two antennas was observed to be below –12 dB across the entire operating bands, and a maximum isolation of –20.2 dB was recorded at the null point. Furthermore, due to the radiation pattern diversity of the two antennas, the envelope correlation coefficient (ECC) remains below 0.1 throughout the bands, indicating excellent diversity performance. These characteristics make the proposed MIMO antenna a strong candidate for 5G applications requiring high isolation and low correlation.