Low-profile MIMO antenna for sub-6G smartphone applications with minimal footprint: an SVM-guided approach

This paper investigates the performance of a low-profile 8 x 8 multi-input-multi-output (MIMO) antenna with zero ground clearance, designed using an intelligent antenna recommender system. A dissimilar antenna pair is employed to achieve multi-band resonance and enhance isolation for sub-6G mobile communication. The primary antenna is a loop antenna resonating at n77, n79, and n46 bands, designed with the aid of a model developed using a support vector machine (SVM). The auxiliary antenna is a modified monopole resonating at n78 and n79 bands to minimize the antenna footprint on mobile devices. An eight-antenna MIMO array is fabricated, and measured results demonstrate that the proposed antenna has a reflection coefficient of less than - 10 dB at 3.5, 3.7, 4.5, and 5.2 GHz, with diversity gain and isolation greater than 9 dBi and 15 dB, respectively. SAR analysis conducted on a human head model shows a maximum SAR value of less than 1.6 W/kg at all sub-6G bands, compliant with FCC standards. The proposed MIMO antenna offers a viable solution, even when integrated with a battery and display, without occupying internal space within a mobile phone.