Research On Substrate Integrated Waveguide Leaky-Wave Antenna With Continuous Beam Scanning Functionality

The research and design of the leaky-wave antenna(LWA)is always a hot topic.Leaky-wave antenna has been a focus for concern and it has a hign radiation gain,a high directivity,and a frequency-dependent beam scanning ability.As a plane waveguide structure,the substrate integrated waveguide(SIW)provides convenience and vitality in the design of leaky-wave antenna due to low profile,compact stucture,and easy fabrication.This thesis introduces the basic principle of the leakywave,discusses the design of the SIW leaky-wave antenna and researches the composite right/lefthanded(CRLH)structure.The beam scanning range is one of the most concerned issues in LWA design.Early LWAs scan only forward or backwardas frequency goes up,but can not scan at broadside,which is due to the open-stopband(OSB)effect.Based on the research of the traditional periodic LWA,the thesis analyses the cause of OSB,in which the reflection coefficient is increased and the gain drops drastically.The thesis analyses and proposes two methods to suppress OSB.One is unit impedance matching,the other is balance condition of CRLH.Then LWAs can scan continuously from backword to broadside to forward.The main work of this thesis is summarized as follows:(1)A SIW space harmonic LWA is designd,which can scan continuously.The unit of the LWA adds a longitudinal slot to the transverse slot of the periodic LWA to realize impedance matching to suppress OSB at broadside.The LWA scans continuously from backword to broadside to forward and has high gain.The gain at broadside is high.The continuous beam scan from-30? through broadside to 25? in the operating frequency.The highest simulated gain achieves 15 dB.(2)The thesis analyses the miniaturization of the LWA,introduces the principle of the half mode substrate integrated waveguide(HMSIW)and compare gains of different sizes of grounds.A folded HMSIW LWA is proposed based on(1).The transverse size of the LWA is reduced to realize miniaturization and reduce the energy leakage from the open boundary in HMSIW.The highest measured gain achieves 13 dB.(3)A novel SIW LWA with OSB suppression is proposed.The unit consists of a longitudinal slot and a via to to realize impedance matching to suppress OSB.The LWA can scan continuously from backword to broadside to forward.(4)A CRLH LWA is proposed.While the periodic LWA has a large longitudinal size,CRLH LWA is compact because the resonant frequency is independent of the physical length.The LWA is double periodic and the periodicity is far smaller than wavelength.The compact structure makes the overall size only 2.5 wavelength.The LWA scans backward in the left-handed region and forward in the right-handed region.The LWA has no OSB at broadside and can scan continuously.The continuous beam scan from-30? through broadside to 30? in the operating frequency.All LWAs proposed above are processed and measured.Simulated and measured results are compared to verify the consistency.