Research On Novel Planar MIMO And Filtering Antennas

With the rapid development of wireless communication technology,the applcaiton of MIMO(Multiple-Input Multiple-Output)technique has been increasingly extensive.As a result,the requirement for the performance of MIMO antennas is continually improving.Besides,in recent years,more and more RF(radio frequency)devices with different functions are integrated on a limited circuit board,and the design of integrating multiple independent devices into a single component has been obtained much attention as it can greatly miniaturize the system.The filter and the antenna are the key components in most of the communication systems.If they are integrated into a single component,called filtering antenna,it can be greatly helpful to miniaturize the RF front ends.Furthermore,since the MIMO antenna is composed of multiple antenna elements,integrating the MIMO antenna and the filtering antenna into the MIMO filtering antenna must reduces the size and cost of the system more significantly.Thus,some researches which focus on high-performance planar MIMO antennas,filtering antennas and MIMO filtering antennas are carried out in this paper.The main innovative works are summarized as follows.?.Design of MIMO slot antennas.A wideband U-shaped stepped slot antenna element is first proposed,and then a two-element MIMO antenna system is developed.Compared to the previous slot MIMO antennas,the proposed antenna shows the merits of wide bandwidth and compact slot size.Next,a new design for the microstrip-fed slot antenna with directive radiation pattern is presented.The proposed slot antennas with compact size and high directivity is very suitable to be applied in MIMO arrays.Experimental results exhibit that such MIMO array shows the merits of high isolation as well as compact size.?.Design of filtering slot antennas.A novel design of broadband filtering slotline antennas excited by multi-mode resonators is proposed.Two types of broadband filtering slotline antennas respectively excited by stub-loaded and crossed resonators have been designed.Compared to the tranditional slot antennas,the proposed antennas show the merits of broader impedance bandwidth and good filtering performance.?.Design of microstrip filtering antenna arrays.First,a design of filtering microstrip antenna array with arbitrary power-distribution is presented.Based on this method,two types of eight-element filtering antenna array with uniform and tapered power-distribution among the elements have been designed.Compared with the uniform filtering antenna array,the one with tapered power-distribution features a lower sidelobe performance.This is the first time a filtering antenna array with reduced sidelobe level has been presented.Next,a novel structure of differential filtering antenna array is proposed.It is the first time that a differential filtering antenna array has been designed.Without any additional measures,the proposed differential filtering antenna array show intrinsically high common-mode rejection.?.Design of wide-stopband filtering MIMO antennas.Two harmonic suppression techniques respectively based on quarter-wavelength resonators and terminated coupled lines are first proposed.The former technique shows the merit of not only simple structure but also wide stopband,while the latter can provide a much wider stopband compared with other techniques.Next,a wide-stopband filtering MIMO antenna is designed based on the latter technique.The proposed filtering MIMO antenna array features wide stopband and high isolation between elements.