A Study Of MIMO Systems For Handheld Devices

With the consumers’ increasing demand for high-performance wireless communication, wireless communication technology is developing rapidly with the goals of achieving large channel capacity, high transmission rate and high reliability. Due to the difficulties of solving these problems with the traditional technology, the Multiple-Input Multiple-Output technology emerge as a new technique to attack these problems. The MIMO system can increase the transmission rate and channel capacity without sacrificing additional frequency spectrum and transmitted power, and has been recognized as one of the key technologies in future wireless communication systems. However, due to the limited space of the mobile terminals, the coupling between the antennas increases gradually with the increasing antenna numbers. The major challenges for a MIMO antenna system are to realize wide band width, miniaturization in size, and high isolations among the antenna elements. In this paper, the MIMO antenna systems for handheld terminal with the size of 136mm × 68.8mm × 1mm are investigated. The main contributions are as follows.1、We have designed a MIMO antenna element of the dimensions 10mm×10mm×5mm which is the smallest volume so far reported, covering the 5G frequency bands 1880MHz-1920MHz and 2300MHz-2620MHz for GSM1900, LTE2300,2.4-GHz WLAN and LTE2500. Based on this antenna element, four types of compact MIMO antenna systems for the mobile handset are studied. The MIMO antenna system is built on a FR4 substrate of the size136mm×68.8mm×1mm. More than 10dB isolations have been achieved by pattern diversity without using decoupling circuits. These handset MIMO antenna systems have high isolation, high efficiency and low envelope correlation coefficient, proving the feasibility of the design. The effects of element numbers and configurations on the system performance are also investigated.2、In order to including the GSM900 communication frequency into the MIMO antenna systems, we design two compact antenna elements of the dimensions 15mn×15mm×5mm and 13mm×13mm×5nm, covering the frequency band 890MHz- 960MHz and 1880MHz-2620MHz for GSM900, GSM1900, LTE2300,2.4-GHz WLAN and LTE2500. Using these antenna elements, two types of compact MIMO antenna systems for mobile are studied, The MIMO antenna system is built on a FR4 substrate in the size of 136mm × 68.8mm × 1mm. More than lOdB isolations have been achieved by pattern diversity without using decoupling circuits. These handset MIMO antenna systems have high isolation, high efficiency and low envelope correlation coefficient, proving the feasibility of the design, the effect of element numbers on the system performance is also investigated.