Isolation enhancement in a compact open-slot MIMO antenna using folded slit paths for sub-6 GHz smartphone applications

Abstract

Abstract An integrated multi-feed MIMO radiating element is presented for sub-6 GHz smartphone wireless communication applications. The radiating element is implemented on FR4 substrate having overall dimensions of $$150 \times 70 \times 1.6\,\textrm{mm}^3$$ , which is approximately equivalent to $$2.9\,\lambda \times 1.35\,\lambda \times 0.03\,\lambda$$ at $$5.8\,\textrm{GHz}$$ . The radiating element evolves from a baseline open-slot configuration to a straight-slit structure and finally to a folded-slit geometry. The proposed folded-slit decoupling techniques effectively interrupt the dominant surface-current coupling path between adjacent antenna elements, thereby improving isolation while maintaining a compact antenna profile. The presented antenna achieves an impedance bandwidth of 5.1– $$5.8\,\textrm{GHz}$$ with a reflection coefficient satisfying $$|S_{11}| < -10\,\textrm{dB}$$ . The coupling between radiating elements remains below $$-\,20\,\textrm{dB}$$ . Envelope correlation coefficient remains under 0.01, demonstrating superior diversity characteristics, while the diversity gain is approximately $$10\,\textrm{dB}$$ . The channel capacity loss approaches zero near the operating frequency, indicating minimal loss in data transmission capability. Additionally, the antenna exhibits a realized gain between 2.5– $$2.7\,\textrm{dBi}$$ , providing satisfactory radiation efficiency. The presented results suggest that the antenna configuration is well suited for compact, sub-6 GHz compact platforms supporting high-data-rate WLAN/Wi-Fi communications, multi-stream MIMO transmission.