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

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.