Researches On Millimeter-wave Antenna Element And Phased Array With Filtering Property

At present,the fifth-generation mobile communication（5G）technology has become a global hotspot,posing new challenges to communication systems in terms of miniaturization,low power consumption,and multi-functionality.The RF front-end system is an indispensable part of the communication system,and its performance improvement is of great significance to the entire system.In general designs,the filters and antennas in the RF front-end system are usually designed separately and then directly cascaded,which greatly increases the size and complexity of the RF front-end and brings additional insertion losses.Especially in the millimeter-wave frequency band,the Q value of a filter is too low to be integrated with a chip,and a single package also faces the problem of multiple interconnections with an antenna and a chip,resulting in large losses.In addition,the coexistence of 5G systems and 2G/3G/4G systems is a trend,but serious mutual interference will exist due to limited space of base stations and close distances between antennas in different frequency bands.The filtering antenna can realize both filtering and radiation at the same time,which provides a new solution for the optimal design of RF front-end systems and the problem of mutual interference in multi-band communication systems.Based on above motivation,this thesis has carried out in-depth researches on the integration of millimeter-wave antenna with the filtering property,and it has proposed the three millimeter-wave filtering antenna elements which can achieve better filtering performance as well as good radiation performance.Accordingly,two millimeter-wave phased arrays integrated with the filtering function were developed to achieve wide-angle scanning performance.The main work is given as follows:1.Millimeter-wave dual-polarized filtering antenna based on metasurface.Based on characteristic mode analysis of metasurface structure,a new filtering method integrated on metasurface antennas is proposed.A radiation null at upper stopband is introduced by inspiring one out-of-band mode of the metasurface structure,while another null at lower stopband is introduced by loading several grounded stubs under the metasurface structure.By providing two kinds of arrangement of the metasurface and the feeding slots,two dual-polarized millimeter-wave filtering antennas with high out-of-band suppression（30d B）and wide stopband suppression up to 58GHz are respectively realized.Due to the use of the multi-resonant modes of the metasurface itself,no additional filtering structure is introduced,and the parasitic structure is located inside the antenna,which does not occupy extra space.The proposed antennas can achieve better filtering performance with high integration and low power consumption.2.Millimeter-wave dual-polarized filtering phased array for 5G applications.In order to meet the spurious suppression requirements of the 5G millimeter-wave communication system,the proposed filtering antenna element with wide stopband suppression is miniaturized,and the size is reduced to 0.33λ₀.The miniaturized element is used to construct a millimeter-wave wide-angle scanning phased array.It can not only achieve large beam-scanning angle of±46°among 24.25GHz and 29.5GHz,but also maintain stable filtering performance while scanning.The lower stopband suppression level is 16d B,the upper stopband suppression level is 14.5d B,and the upper stopband can be suppressed to40GHz.3.Millimeter-wave filtering antenna with high selectivity and its applications in phased array for wireless energy transmission.Aiming at the requirements of millimeter-wave wireless energy transmission,a high-selectivity and high-suppression filtering antenna element is proposed.The patch antenna fed by a coupling slot can achieve a high out-of-band suppression with multiple radiation nulls,by adding a parasitic patch,a split-ring slot,a grounded pin,and two shorted stubs.Meanwhile,the working principle is analyzed by using an equivalent transmission-line circuit model.Using LTCC packaging technology,the element is expanded to a 4×4 array to realize a wide-angle scanning filtering antenna array.The array not only has filtering performance of high suppression of over 23d B up to 35GHz,but also achieve large beam-scanning range from-58°to+60°.The in-band radiation efficiency is higher than 75%,the out-of-band radiation efficiency is lower than 7%.