Design Of Novel Planar Multi-element Antennas

As two kinds of basic elements of multi-element antenna,the electric and the magnetic element have similar radiation performance.Through combination of the elements and flexible design of the structure,antennas with various performance can be realized.According to the different relative position of electric and magnetic elements and the various source phase among them,the antenna can achieve diverse radiation performance such as multi-polarization.While the same electric element or magnetic element can be arranged regularly to form a quasi-frequency independent structure which can also achieve broadband performance.In addition to the excellent and diverse radiation performance,the antenna structure is also developing towards planarization and integration.The magnetic element can be constructed by the metal floor slotting and the electric element can adopt printed dipole or planar monopole structure in order to realize low profile printing process.In this paper,planar monopole and slot antenna elements are combined on the same plane to realize the dual polarization with magnetoelectric complementary structure.Through the logarithmic periodic arrangement of the planar monopole elements,not only wideband end-fire performance can be achieved but also the height of antenna can be greatly reduced.The research contents are as follows:1)Two kinds of printed magnetoelectric complementary dual polarization antennas are designed.The first structure is planar monopole combined with closed slot which have orthogonal polarization directions.By means of orthogonal current excitation,the antenna can radiate two orthogonally polarized waves.Based on the complementary screen principle,the second structure-half-slot and planar monopole,can also achieve similar performance to the first structure,while further reducing the size of the antenna.These two dual-polarization antennas have simple structure,low profile,light weight which are easy to be processed.Both of them can achieve high polarization purity and design flexibility.2)A planar log-periodic monopole antenna with backward firing is designed.Low profile logperiodic element antenna can be constructed by adopting planar monopole as array elements arranged according to the log-periodic rule.Combined the feeding structure of exciting from the end of short element of traditional log-periodic dipole antenna and the radiation structure of the planar logperiodic monopole antenna,the bandwidth can be further expanded to more than three octaves.What's more,the method to improve efficiency of simulating multi-element antennas is provided during the design process.