Research On The Coupling Of Terminal Antennas For MIMO System

Great changes have taken place in wireless communication during the last 30 years; it doesn't only have great impact on people's daily life, but also on commercial activities. The creative technology, namely Multiple input Multiple output(MIMO),has provided a novel solution to the problem of both high capacity and high reliability in the new generation wireless communication systems.MIMO methods make use of multiple—antenna at both the transmit and the receive side of the radio link to multiply the capacity and reliability over more traditional wireless communication systems. Antenna is one of the important component in wireless communication quality. The rapid development of wireless communication technology puts higher request on terminal antenna. Therefore, research on antenna which is tiny, multi-frequency and compatible in MIMO system has prodigious significance.PIFA satisfies the requirements of the system with small size, little backward radiations, broadband and mulit-frequency bands. So PIFA is widely used in communication terminal equipment. The thesis is on the multi PIFA antennas for MIMO system. Based on the coupling theory of MIMO antenna and low profile antenna array is introduced with the PIFA antenna element. The antenna is intended to operate at the following frequency bands: 885-915MHz, 1760-1870MHz and 2450-2510MHz. The distance between the PIFAs is severely reduced to less than half wavelength. To improve the isolation between the two closely packed antennas, two methods are proposed. One way is to use a suspended neutralization strip which is inserted and physically connected to the antenna elements to improve isolation. The other way is to use FR4 to reduce coupling. The simulation results show that the isolation over the operating band is more than 15dB without affecting the radiation patterns obviously, which proves the designs valid.