Research On Multi-Band Fabry-Perot Resonator Antennas

With the rapid development of modern radar,satellite communication and air transportation,antennas play a vital role as the more important equipment for transmitting and acquiring information.The Fabry-Perot(FP)resonant cavity antenna has attracted extensive attention since it was put forward,because of its simple structure,small physical size,low profile and easy fabrication.Although it has such obvious advantages,the inherent defects of this kind of antenna,such as narrow bandwidth and fixed beam direction,limit its application range.Therefore,it is of great academic and application value to explore the new FP resonator structure and research FP resonator in increasing antenna bandwidth and realizing dual-band or multi-band performances.This thesis conducts in-depth research on the design method of resonant cavity antenna with multiband and linear-circular polarization conversion performances.The main contribution can be summarized as follows:1.A method of combining positive phase gradient partial reflection surface with wideband linear-to-circular polarized conversion surface is proposed to realize wideband circularly polarized radiation of the resonant cavity antenna.Firstly,a partially reflective surface with positive phase gradient is designed.Square metal rings are printed on the upper and bottom surfaces of the substrate,and the side lengths of the two metal rings are adjusted to make the partially reflective surface have wideband characteristics.Then,a meta-surface element which can realize wideband linear-to-circular polarized conversion is designed.The transmission phase of this element can be adjusted independently,therefore the meta-surface composed of this element can realize wideband linear-to-circular polarized conversion.Finally,the designed conversion meta-surface is loaded above the wideband Fabry-Perot resonator to realize high-gain wideband circularly polarized radiation.2.A design method of dual-band and dual-polarized resonant cavity antenna using doublelayer partially reflective surfaces with passband and stopband characteristics is proposed.One layer of partially reflective surface adopts a linear-to-circular polarized conversion structure with independently adjustable transmission/reflection coefficient to realize highgain circularly polarized radiation;The other layer of partially reflective surface adopts a symmetrical structure to realize high-gain linearly polarized radiation.Compared with the traditional dual-band dual-polarized resonator cavity antennas,this method can realize linearly and circularly polarized radiations simultaneously by using two independent cavities.The measured results show that the peak gains of antenna reach 15.3 d Bi with linearly polarized radiation at 5.6 GHz and 16.1 d Bic with circularly polarized radiation at 9.4 GHz.3.A tri-band Fabry-Perot resonant cavity antenna is designed in this thesis.A double-layer partially reflective surface with passband and stopband characteristics is designed to realize tri-band operating characteristics.A dual-band microstrip patch antenna and dipole antenna are used as feeding antenna.A compound resonant cavity antenna is designed by using the double-layer partially reflective surface and the feeding antenna.The simulation results show that the tri-band resonant cavity antenna can achieve the peak gains of 14.4 d Bi,17.15 d Bi and 15.8 d Bi at 6.15 GHz,7.15 GHz and 9.24 GHz,respectively.