Design And Research Of Leaky Wave Antenna Composed Of Composite Right/left-handed Transmission Line

In radar and wireless communication system,the array antenna usually adopted phase shifter or digital beam formed by control to realize scanning beam.However,this method of scanning beam occupied big usage space and high cost,which didn't accord with the design philosophy of miniaturization and low cost.The leaky wave antenna composed of composite right/left-handed transmission line designed in this article adopted no phase shift method to realize scanning beam of the antenna.The beam direction changed with the frequency and altered the limitation that traditional leaky wave antenna could only scan the former half-space,expanding the scanning area to the total space and energy in each beam direction being rather balanced.Its panel adopted the most common FR-4 panel and the dimension was only0.69?₀×0.093?₀,meeting the demands of miniaturization and low cost.Firstly,this article reviewed the basic theory of microstrip antenna and theory of transmission lines,and analyzed electromagnetic propagation characteristic and principle of left-handed materials.Then,it emphatically introduced the basic principle of composite right/left-handed transmission line,constituting its basic physical model of transmission structure by artificially uploading shunt inductance and series capacitance in the common transmission line,and further studied its basic circuit model and physical structure.By considering impedance of transmission line in the equivalent model of the ideal composite right/left-handed transmission line and building an equivalent circuit model with the admittance of ground connection plane,this article proposed a parameter extraction method based on resonant frequency to exactly describe the structure of multisection composite right/left-handed transmission line,and studied its consistency between physical model and equivalent circuit model by simulation software so as to verify this new parameter extraction method proposed by this article.According to this new equivalent model,this article designed and produced three leaky-wave antennacomposed of composite right/left-handed transmission line,and measured their S parameters with network analyzer.Results showed that the measuring results of full wave simulation model,circuit simulation model and antenna entitieshave favorableconsistency.To further study the interspacescanning beam characteristic of leaky-wave antennacomposed of composite right/left-handed transmission line,this article respectively carried out simulation and physical tests of distant fieldradiation characteristic to the three leaky-wave antennas.Finally,it drew the conclusion that leaky-wave antennacomposed of composite right/left-handed transmission line under equilibrium state has more symmetricalradiation characteristic in different beam directions.