Research On Circular-polarized Antenna Based On Composite Right And Left-hand Transmission Line

With the development of satellite communication,remote control and telemetry technology,the expansion of radar application range and the need to track and measure high-speed targets under various polarization modes and climatic conditions,the single polarization mode is far from satisfied,and the application of circular polarization is very important.However,the traditional microstrip circularly polarized patch antenna is still larger in size for modern wireless devices,especially in the low frequency part.In recent years,left-handed materials have begun to gain more and more popularity in the fields of solid state physics,material science,optics and applied electromagnetism due to their abnormal electromagnetic properties.The backward wave effect of the left hand material and the forward wave effect of the right hand medium should be combined,the antenna with compound left and right hand transmission line structure can break through the limit of half wavelength and realize the miniaturization of microstrip antenna.Taking this as an opportunity,this paper presents a new type of composite left and right hand transmission line structure,which is applied to the design of circularly polarized antennas with single and double frequency bands:1.A new composite left and right hand transmission line structure for microstrip patch antenna was designed.fed by a microstrip line,a rectangular radiation patch is used on the front side,a double spiral groove and a metal through hole are introduced in the center of the rectangular patch,and a long strip metal patch is introduced on the back side.the three parts together realize a new type of CRLH-TL structure and realize the left hand characteristic of double negative relative permittivity and relative permeability.2.A circularly polarized antenna based on the compound left and right hand transmission line structure applied to the 2.7 GHz band is proposed.Two identical rectangles were cut off in the lower and upper right corners of the front radiation patch to realize the circular polarization radiation performance of the antenna.the overall size of the final antenna patch is 50 mm×40 mm×1.6 mm,and the relative permittivity and relative permeability of the antenna are deduced by using the NRW transmission/reflection method to realize the double negative characteristics in the working frequency band.the impedance bandwidth and the axial ratio bandwidth of the antenna are 32.4%and 6.90%,respectively.3.A dual-band circularly polarized microstrip patch antenna based on a new composite left and right hand transmission line structure is designed.using the proposed new composite left and right hand transmission line structure,the overall size of the final antenna patch is 0.23?0×0.18?0,which realizes the miniaturization of the antenna.The central frequency of the antenna is 1.41Ghz and 2.9Ghz,the working bandwidth of S11<-10dB is 60MHz and 480MHz respectively,and the 3dB axial ratio bandwidth of the antenna is 2.63%(1.39Ghz-1.42Ghz)and 4.72%(2.48Ghz-2.60Ghz)respectively,to achieve circular polarization in the L and S bands.This antenna is compact,and easy to processing.