Isolation Enhanced Compact Dual-Mode 4-Port MIMO Design Using Slot-Based Switchable DGS Decoupling Filters

A compact MIMO antenna with enhanced isolation and the ability to switch the frequency bands is an attractive candidate for the current multifunctional high-speed portable wireless devices. To achieve this objective, a simple and novel compact dual-mode 4-port MIMO configuration for WiMAX and WLAN standards has been introduced in this work. The compactness of the MIMO geometry (34 mm × 34 mm) is due to compact switchable curve-shaped monopoles arranged closely over a loop-shaped continuous ground plane. The ground plane is defected by etching open-ended slots to suppress the surface current flow between the elements. As antenna elements switch between mode-1 (WiMAX band) and mode-2 (WLAN band), the DGS slots are also switchable to enhance isolation across both bands. The switchable DGS slots function as bandstop filters and thus isolate the elements by 40 and 41 dB in the accomplished frequency bands. The intented MIMO antenna reports a − 10 dB return loss bandwidths of 400 MHz (3.3–3.7 GHz) and 1100 MHz (4.75–5.85 GHz) in mode-1 and mode-2, respectively. The diversity metrics of envelope correlation coefficient < 0.002, diversity gain ≈ 10 dB, total active reflection coefficient < − 10 dB, and channel capacity loss < 0.4 b/s/Hz, ensure excellent diversity/MIMO performance. The optimized 4-port MIMO configuration is fabricated, and measured results are compared with the simulated ones to validate the introduced technique. The MIMO antenna's compact form factor and excellent antenna/diversity characteristics confirm its potentiality for use in portable multifunctional wireless devices.