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Abstract
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A novel broadband Matching and Decoupling Network (MDN) for symmetric two-element array of microstrip patch antennas is proposed. As a distributed multiple inductive-capacitive loading, this MDN employs two groups of parallel shorting posts (vias) on the non-radiating edges of the high-coupled patches with a very-low edge-to-edge distance.
This MDN excites two controllable new modified resonant half-modes, TM1/2,1 and TM3/2,0, whose aggregation provides a well-matched broad bandwidth with broadside pattern. Furthermore, a reasonable offset between these two groups of vias helps obtaining a balance between the mutual capacitive and inductive couplings and then a broadband high isolation across the overlapped bandwidth without using the conventional large isolating structures. A resonator-based equivalent-circuit model including different mutual and cross couplings is proposed and discussed to study the coupling mechanism between the modes and antennas.
Finally, the measurement proves a bandwidth of 9.8% (3.38~3.73GHz) with an enhanced isolation of over 27dB. A fair comparison with the state-of the-art approaches is drawn, and greatly reduced spatial correlation (with envelop correlation coefficient (ECC) of less than 0.06) and over 72% total efficiency (with 25% increase) make the proposed design appropriate for 5th-generation (5G) multi-input multi-output (MIMO), and the other sensitive bi-element systems.
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