A novel quad-port MIMO antenna with slotted ground and resonator structure for ultra-wideband, X-band, and Ku-band applications

Abstract

A new four-port multiple input multiple output (MIMO) antenna has been designed for ultra-wideband (UWB) use, functioning within a frequency spectrum from 3.27 to 18.38 GHz. The antenna elements are arranged orthogonally to minimize mutual interference in the proposed design. The slotted ground plane not only serves as a basic impedance matching network but also acts as a decoupling structure, providing high isolation. The proposed MIMO antenna, measuring 0.994λg × 0.994λg with monopoles at 0.415λg × 0.548λg and 0.307λg spacing, utilizes strategically placed defected ground structure resonators to enhance isolation at lower frequencies. At 11.77 GHz, it achieves a peak gain of 6.95 dBi, with isolation over 20 dB, an envelope correlation coefficient below 0.005, a diversity gain of around 10 dB, a mean effective gain ratio of 3 dB or lower, a total active reflection coefficient under −8 dB, and a channel capacity loss of 0.4 b/s/Hz or less across the spectrum. By mitigating strong coupling between closely spaced radiators and ensuring stable omnidirectional radiation from broadband monopoles, the antenna sustains robust operation throughout the entire spectrum. Its compact Rogers 5880 substrate enables integration into portable platforms without compromising bandwidth or pattern diversity. Owing to its high isolation, low correlation, and wideband stability, the proposed MIMO antenna is well suited for UWB communications, sub-6 GHz 5 G devices, Internet of Things terminals, and short-range sensing applications.