Theory Analysis And Design Of Novel Leaky-Wave Antennas

Leaky wave antenna(LWA)is a kind of traveling wave antenna,which is based on the traveling wave waveguide structure.LWAs have been widely used in the practical engineering field.Based on theory analysis of the radiation mechanism of the leaky wave antenna and the transmission characteristics of SIW(substrate integrated waveguide),DIL(dilectric image line)and SSPPs-TL(surface plasmon polariton transmission line),various LWAs are proposed combined with the unique design methods of the uniform LWA and the periodic LWA.The main content and innovations of this dissertation are concluded as follows:1.Based on the fast wave characteristic of the main mode of the SIW,a dual-band LWA and a wide scanning angle LWA are designed.(1)The proposed dual-band LWA consists of two back-to-back quasi-uniform LWAs.A feeding network with duplex property provides power to the two arrays.Feeding power travels through the upper array in the low band and passes through the lower array in the low band,then the scanning beams in two different bands are realized.(2)A wide-angle LWA based on SIW is designed by bending the SIW in the form of a serpentine line and increasing the equivalent relative dielectric constant of the bent SIW.By increasing the meander length,the guided wave path is extending.So,the ratio of angle and frequency of the proposed LWA is increased,that is,the wider scanning region is realized in a narrower frequency band.2.DIL is a slow wave,which supports surface waves and has no radiation characteristics.Two DIL-based periodic LWAs are proposed by introducing periodic discontinuous units along the DIL,which both works in the fast-wave region of the n=-1 order harmonics.The two proposed antennas enable continuously sweep from the backward region to the forward region continuously.For one LWA,the unit cell is with “H-shaped” groove engraved on the metal ground of the DIL,and the radiation beams can coverage 103° and the variation of gain is only 1.3d B.For the other LWA,the unit cell is with “H-shaped” metal patches in the top surface of the DIL,which has high loss constant.So,the antenna just with three unit cells can achieve high-efficiency radiation.And the beam scanning range is 71° and the gain varies in1.9 d B.3.Three LWAs based on SSPPs-TL are designed based on the fast-wave radiation and slow-wave radiation mechanisms.One proposed antenna based on fast-wave radiation mechanism has frequency-contrlled scanning beams;and the other proposed antenna based on slow-wave radiation mechanism have fixed beams.(1)A periodic LWA based on the microstrip SSPPs TL is proposed.Based on the fast-wave radiation mechanism,the proposed antenna can achieve wide-angle scannig beam by the uses of a n=-1 harmonic wave in its fast-wave radiation region.The basic waveguide of the antenna is the microstrip SSPP-TL,which is a two-conductor SSPPs waveguide structure with metal floor fed by the microstrip line.Compared with the LWA fed by single-conductor SSPPs waveguide structure,the proposed antenna has simple feed structure and single beam.(2)A Parallel SSPPs-TL fed by a microstrip line is proposed,consisting of two parallel single-conductor SSPPs-TL in two faces of the dielectric substrate.The parallel SSPPs-TL is a slow-wave waveguide that can support travelling waves with low loss and the dispersion characteristics can be controlled by the height of the grooves,which is similar to the property of the single-conductor SSPPs-TL.(3)A LWA based on the parallel SSPPs-TL is proposed,which is composed by periodically introducing open metal stubs in the top and bottom surfaces of the parallel SSPPs-TL.The proposed antenna can radiate backward endfire beams in the slow-wave radiation region of n=-1 order spatial harmonics.At the same time,by tapering the radiation stubs,not only the impedance matching of the antenna can be improved greatly,but also the radiation patterns of the antenna can be improved greatly with more stable patterns.What's more,a metal reflector is arranged below the endfire antenna,so the endfire beams are reflected to a certain angle on the elevation plane.The angle of inclination changes with the distance between the antenna and the reflective ground.