Abstract
In this article, a miniaturized 4-element frequency reconfigurable multiple-input-multiple-output (MIMO) antenna system is presented. The proposed design is low profile with planar configuration. The design consists of pentagonal slot-based frequency reconfigurable antenna elements. Varactor diodes are used to change the capacitive reactance of the slot. The MIMO antenna system can be tuned over a frequency band covering 3.2 to 3.9 GHz with at least 100 MHz bandwidth within each band. The proposed antenna covers several commercial standards including WiMAX (3.4-3.6 GHz), TDD LTE (3.6-3.8 GHz), and Wi-Fi 802.11y (3.65-3.7 GHz), along with several other bands. The proposed design was realized on a board of dimensions 60 x 120 mm(2). The isolation between adjacent antenna elements is improved using slot-line based defected ground structures (DGS). The antenna maintains a minimum isolation of 10 dB in its entire covered operating bands. The antenna is also analyzed for its far-field characteristics and MIMO performance parameters. The proposed design is suitable to be used in mobile handsets for cognitive radio (CR) platforms.