A Self-Decoupled Antenna Array Using Inductive and Capacitive Couplings Cancellation

The concept of a self-decoupled antenna array using the cancellation of two opposite couplings is proposed in this article. A pair of such antennas can be closely placed with inherent high isolation without using an extra decoupling structure between the antennas. A pertinent equivalent circuit model is presented to illustrate the physical mechanism of this new concept. It is found that the inductive and capacitive couplings between the antennas can be well canceled out with each other by properly adjusting the antenna dimensions. A demonstrating antenna array with a spacing of 0.024 lambda(0) at the working frequency of 3.5 GHz and its counterpart array are first studied. The measured results show that although the proposed antenna array occupies a slightly larger size than its counterpart array, it presents better performance compared with its counterpart antenna array in port isolation (from 10 to 20 dB), total efficiency (from 68% to 80%), and envelope correlation coefficient (ECC) (from 0.14 to 0.04) throughout the desired frequency band of 3.3-3.8 GHz. A 3-D self- decoupled antenna array is designed to show that the proposed antenna can be in a compact form factor. Another self-decoupled array and its counterpart working at 2.14 GHz (long-term evolution (LTE) band 1) are studied through multi-input multi-output (MIMO) over-the-air (OTA) test when the arrays are integrated with an LTE module, showing significant improvement on the data throughput.