Design of compact MIMO SIW antenna with loading circular slot for 5G Sub-6 smartphone applications

The article describes the compact MIMO antenna design having loading circular slot for 5G Sub-6 GHz smartphone applications using SIW. The proposed SIW antenna is realized by loading a circular slot into a Full-Mode Substrate Integrated Waveguide (FMSIW) resonator, which facilitates the excitation of fundamental modes, resulting in enhanced gain in the broadside direction while maintaining a miniaturized size. The antenna's dimensions are 30 × 30 × 1.6 mm³, and it is designed on an inexpensive FR4 substrate, making it suitable for compact handheld devices. To suppress the mutual electromagnetic coupling between antenna elements, an electrical wall is introduced by incorporating a row of SIW vias between them, effectively suppressing electromagnetic wave propagation and enhancing isolation. The antenna operates efficiently across the 3.3–3.6 GHz band, covering key Sub-6 GHz 5G bands. The design demonstrates high radiation efficiency, stable gain, and a low envelope correlation coefficient (ECC < 0.02), making it highly suitable for compact MIMO configurations in next -generation 5G smartphone device.