ABSTRACT This paper presents an ultra‐wideband (UWB) antenna pair for 5G mobile terminals. The antenna pair is composed of two coupled‐fed loop antennas with a common shorted branch, which achieves a compact size. The wideband operation is obtained by meticulously exciting two‐loop modes. Due to the common shorted branch, a good isolation level (> 10 dB) is acquired. Based on four coupled‐fed loop antenna pairs, an ultra‐wideband 8 × 8 multiple‐input multiple‐output (MIMO) array with compact size is conducted and measured. The experimental results show that the MIMO array covers 3.3–7.8 GHz with a relative bandwidth of 81.08%, and the isolation between ports is better than 10 dB. In addition, the measured radiation pattern, total efficiency and ECCs (envelope correlation coefficients) are also discussed.
Ren et al. (Thu,) studied this question.