Planar meandered‐F‐shaped 4‐element reconfigurable multiple‐input–multiple‐output antenna system with isolation enhancement for cognitive radio platforms

In this study, a novel meandered reconfigurable F‐shaped antenna is presented. The proposed design is a 4‐element, dual mode, multiple‐input–multiple‐output (MIMO) antenna system. Frequency agility is achieved using P‐type intrinsic N‐type (PIN) diode switching while frequency tuning is realised using varactor diodes. The proposed design covers wide frequency bands below 1 GHz and is realised on a single substrate. The proposed design is compact and highly suitable to be used in cognitive radio‐based wireless handheld devices. An isolation enhancement technique is applied to reduce the mutual coupling between various MIMO elements. Rectangular defected ground (GND) slots are used to reduce the mutual coupling between horizontally placed antenna elements while staircase type GND plane structure is introduced to enhance the isolation between vertically placed antenna elements. The antenna elements are also evaluated for MIMO performance metrics. The antenna system covers a size of 65 ×120 ×1.56 mm 3 .