Isolation enhancement of compact dual‐wideband MIMO antenna using flag‐shaped stub

A compact dual‐wideband multiple‐input multiple‐output (MIMO) antenna with a size of 36 × 22 mm2 is proposed for portable systems. The proposed antenna consists of two identical monopole antenna elements (MA) which are placed on one side of the substrate. The ground plane with Flag‐shaped stub is placed on the other side of the substrate to reduce mutual coupling and enhance isolation between the antenna elements. It is found out that the Flag‐shaped stub introduced one more coupling path and this coupling path cancel out the original coupling between the MAs. The proposed antenna has two operating wideband of 2.5–2.85 GHz (lower band) and 4.82–6.1 GHz (upper band) owing to the slits and slots that are located besides Flag‐shaped stub. Those slits and slots generate certain resonances and simultaneously notched‐out the initial antenna's band. Combination technique of Flag‐shaped stub with slits and slots contribute to the isolation of better than 18 dB across the lower band and more than 20 dB at the upper band. Instead of good isolation at both bands and compact size, ECC of 0.05 leads the antenna suitability for MIMO multiple standards applications such as LTE, WLAN, WiMAX, and HIPERLAN.