Enhanced Matching and Vialess Decoupling of Nearby Patch Antennas for MIMO System

Simultaneous improvement of matching and isolation for a modified two-element microstrip patch antenna array is proposed. Two simple patch antennas in a linear array structure are designed, whereas the impedance matching and isolation are improved without using any conventional matching networks. The presented low-profile multifunctional vialess structure comprises only two narrow T-shaped stubs connected to feedlines, a narrow rectangular stub between them, and a narrow rectangular slot on the ground plane. This design provides a simple, compact structure with low mutual coupling, low cost, and no adverse effects on the radiation and resonance. To validate the design, a compact, very closely spaced antenna array prototype is fabricated at 5.5 GHz that is suitable for multiple-input-multiple-output systems. The measured and simulated results are in good agreement with 16 and 40 dB of improvements in the matching and isolation, respectively.