Broadband Two-Element Array With Hybrid Decoupling Structures for Multimode Mobile Terminals

A two-element array with high isolation is presented for multimode mobile terminals. The antenna array is composed of two symmetrical antennas and a novel decoupling structure. The antenna element covers the LTE700/GSM900/GSM1900/UMTS/LTE2300/2500 operations. The decoupling structure is embedded between the two broadband antennas, which is a hybrid structure and composed of lumped elements (capacitors) and distributed elements (three pairs of U-shaped slots). By loading lumped capacitors at the edges of the slots, the lengths of the slots are decreased efficiently. By embedding three pairs of U-shaped slots, broadband decoupling is achieved. A prototype of the proposed antenna array was fabricated and tested. The antenna covers the lower bands (704-787 MHz and 880-960 MHz) and the upper bands (1800-2690 MHz) with the definition of 3.5:1 VSWR (5 dB return loss). The measured isolation between the two antennas is better than 11 dB, and the efficiencies at the lower bands and the upper bands are better than 30% and 40%, respectively. The proposed antenna array is easy to find applications in a thin or slim mobile phone which meets the current fashion taste.