Ultrawideband MIMO/Diversity Antennas With a Tree-Like Structure to Enhance Wideband Isolation

A compact printed ultrawideband (UWB) multiple-input multiple-output (MIMO)/diversity antenna system (of two elements) with a size of 35 × 40 mm
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operating at a frequency range of 3.110.6 GHz is proposed. The wideband isolation can be achieved through a tree-like structure on the ground plane. The effectiveness of the tree-like structure is analyzed. Measured S-parameters show that the isolation is better than -16 dB (-20 dB in most of the band) across the UWB of 3.110.6 GHz. The radiation patterns, gain, and envelope correlation coefficient are also measured. The proposed antenna is suitable for some portable MIMO/diversity applications.