Miniaturized Step Impadance Tri-polarization Slot Antenna

Multiple Input Multiple Output(MIMO) is the main research direction of wireless communication technique. Polarization diversity can improve spectrum utilization. In the same volume, theoretically tri-polarization communication system can get three times the channel capacity of unipolar communication system. Especially in rich scattering environment, the co-located electromagnetic tri-polarization antenna can achieve up to six polarization degrees of freedom. This makes tri-polarization antenna has a very broad application prospects.This thesis improved the normal slot antenna,researched the antenna with Stepped Impedance structure radiation slot. At the same time, added sets of slot stub on ground plate of antenna to make the antenna more flexible. It can be easily used in MIMO systems.The main work is:(1)Proposing a design that using the Stepped Impedance structure in the radiation slot of normal slot antenna. Based on the SI theory, using ’H’ size stepped impedance structure and made parameter sweep on one-piece antenna. Through research and analysis, get best chooses of all the parameters which can give the miniaturized antenna best performance. One-piece antenna with 27.2mm(miniaturized 22.7%) radiation slot, simulation result: resonance frequency is 2.45 GHz, operation bandwidth is 330 Mhz,, isolation under-27 dB, cross polar near-20 dB.(2) Proposed a new microstrip feed structure. Using HFSS simulation, we can get the result: Comparing with microstrip probe feed and coaxial probe feed, this new microstrip feed structure can give the antenna wider operation bandwidth. It can be uesd to feeding miniaturized antenna.(3)Using different thickness in dielectric-slab(1.524 mm and 0.812mm), Compared with the normal slot antenna, when the miniaturization is 38%, 1.524 mm dielectric-slab: resonance frequency is 2.45 GHz, operation bandwidth is 100 Mhz, cross polar near-10 d B, isolation is-20dB; 0.812 mm dielectric-slab: resonance frequency is 2.45 GHz, operation bandwidth is 100 Mhz, cross polar near-6d B, isolation is-24dB;Since the environment of microwave unreflected chamber has influence on the cross polar testing. All the cross polar got worse. But the dielectric-slab thickness 1.524 mm of the multi-polarization miniaturized antennas still with features like high polarization purity and isolation and complete radiation directivity pattern which are beneficial to improve the performance of MIMO systems.