Reconfigurable Inverted-F Antenna for MIMO Cellular User Equipment

MIMO (multiple input multiple output) systems are utilized more and more in modern handheld cellular devices. Because of the limited space, the mutual coupling effect between the antennas increases significantly. In order to reduce the coupling between antennas various decoupling and matching networks are implemented. In this work, a concept for reconfigurable inverted-F antenna for MIMO RF frontends in cellular user terminals is proposed. The main component of the system is the RF switch-based IC (integrated circuit), which was manufactured in Infineon 130 nm RF switch technology. The chip reconfigures the physical length of the inverted-F antenna (IFA), making the antenna longer for low-band operation and splitting the antenna in two IFAs for middle/ high band MIMO operation. The proposed concept implements MIMO approach with 19 dB isolation between the antennas at 1.8 GHz while sustaining good efficiency at 900 MHz.