Design Of MIMO Antennas Based On WLAN/WIMAX Wireless Communication System

In recent years, due to rapid developments and wide applications of wireless communication technology, people’s requirements for wireless network become more and more urgent. Wireless Local Area Network( WLAN) and Worldwide Interoperability for Microwave Access( WiMAX) are key technologies in wireless communication. In order to meet the people’s consumption requirements, the transmission rate, transmission distance, and channel capacity in the wireless communication system need to be improved. Multiple-input-multiple-output(MIMO)technology is a good candidate to improve the performance of wireless communication network, but it puts forward higher standards on the antennas. MIMO antenna with miniaturization, multiband and higher isolation is desired in WLAN/ WiMAX systems.In this paper, three kinds of compact MIMO antennas are designed for potentil applications in the WLAN/ WiMAX wireless communication systems.Based on the IEEE 802.11 and IEEE 802.16 series of standards, three printed microstrip MIMO antenna are designed in this work. The first one is a frequency reconfigurable microstrip MIMO antenna. The antenna size is 40×30×1.6 mm3. The presented antenna mainly comprises two frequency reconfigurable antenna elements based on folded-strip dipole. A coupled microstrip line with switch is etched in the ground and makes the dipole a coupling-radiation antenna. By controlling the switch on the coupling microstrip line, one can change the working states of the antenna by virtue of changing the impedance bandwidth. Considering different working states, the working frequencies of the antenna can cover the bands of WLAN/WiMAX. 2.4/3.5/5.8GHz.The second designed antenna is a MIMO antenna based on a monopole antenna. A microstrip monopole MIMO antenna with quite simple structure for wireless universal serial bus(USB) dongle application is presented. This antenna comprises a folded-strip radiator and a rectangle ground. The antenna size is 42×38×0.580 mm3. The proposed antenna is simple in structure and easy for integration with the USB circuits. Moreover,it reveals good characteristics in radiation performance when working at the 2.4/5.2/5.8GHz WLAN bands.The third antenna is a printed MIMO antenna with loaded lumped elements,whichcan be applied in WIMAX system. The MIMO antenna is composed of four element antennas. Its size is only 160×40×1.6 mm3. The proposed antenna employs lumped elements and uses ground as a radiator to control resonance frequency. The antenna can be applied in 3.5 GHz WiMAX system.Decoupling strips and slots are introduced to improve the isolation. The isolations of the three antennas in their working bands are all above 15 dB.