Designs Of Leaky Wave Antenna Based On Spoof Surface Plasmon Polaritons

Spoof Surface Plasmon Polaritons(SSPPs)has strong restraint on electromagnetic waves,and the SPPs transmission line is a slow wave transmission line of single conductor.Using the dispersion effect of SPPs,we can design all kinds of microwave devices,such as filters,antennas and so on.Leaky wave antenna,as a typical representative of traveling wave antenna,has attracted extensive attention because of its unique frequency beam scanning characteristics.Leaky wave antenna was first realized by slotting on metal waveguide,which has the disadvantages of large volume and high cost.With the emergence of all kinds of planar transmission lines,the research of leaky wave antenna has been given a new impetus.In this paper,several leaky wave antennas are studied and designed by combining the theory of SPPs transmission line and leaky wave antenna.The main work of this paper is as follows:(1).A broadband circularly polarized leaky wave antenna based on SSPPs is designed.The antenna adopts a single-layer conductor structure and is fed by a flared coplanar waveguide.According to the sequential rotation feed theory,four rectangular patches are selected to form a quaternion array by rotation.Eight groups of such radiation patches are periodically loaded on both sides of the SSPPs transmission line to obtain additional momentum to modulate the SPPs surface wave into circularly polarized space radiation.In the working frequency band of 5.4-9GHz,the antenna realizes backward to forward continuous frequency beam scanning,and the scanning angle is about 87 degrees.The axial ratio of the antenna is less than 3d B between 6.5-8.7GHz,the relative bandwidth of the axial ratio is about 30%,and the circular polarization scanning angle is about 50 degrees.The average gain of the antenna is about 9.5d Bi and the radiation efficiency is more than90%.(2).A narrowband circularly polarized leaky wave antenna based on sspps is designed.Using the cut-off effect of the open resonant ring on the current,a perturbation is formed.Circular polarization is formed by placing two open resonance rings with the same size,one quarter wavelength apart and perpendicular to each other as radiation patches in a radiation unit.The leaky wave antenna uses six groups of such radiating elements,which can realize backward to forward continuous beam scanning with the increase of frequency in 3-6GHz,and maintain the average gain at the side firing position of4.8GHz.The antenna can realize a narrow-band circular polarization in the frequency range of 5.1-5.6GHz.The average gain of the antenna is about 10 dbi,and the radiation efficiency is high,about95%.(3).A full space scanning leaky wave antenna based on sspps is designed.Firstly,the SPPs unit and transmission line are designed,and the way to realize full space scanning is analyzed through the monopole array.The SPPs transmission line and the semicircular three-dimensional loaded radiation patch are designed to be equivalent to the monopole radiation unit.The whole leaky wave antenna is a monopole array composed of twelve such radiation units.The leaky wave antenna can realize a nearly full space continuous beam scanning in the frequency band range of 9.8-13.3GHz,and the average gain of the antenna is about 9dbi.And we also designed a group of planar leaky wave antennas as a comparison to reflect the advantages of the antenna’s large scanning angle.The above designed antennas have been theoretically analyzed and simulated,and the antennas in(1)and(3)have been measured to verify the feasibility of the design.