Research And Design Of Multi-band Circularly Polarized Antennas

The current mobile communication system requires high-speed data transmission,while the integration of the terminal device has put forward higher requirements.Therefore,antenna in the wireless communication terminal also develops towards broadband,multifrequency and miniaturization.In the fight against electromagnetic interference,the polarization orthogonality of circularly polarized waves is beneficial to suppress the signal fading caused by multipath effect and ionospheric Faraday effect.However,common microstrip circularly polarized antennas have narrow bandwidth and single frequency,while broadband and multi-frequency antennas have great advantages in enhancing spectrum utilization and expanding channel capacity.Therefore,this paper addresses the microstrip circular polarization antenna to expand bandwidth and multi-antenna multi-frequency technology,specifically including:1.Broadband multi-frequency circular polarization antenna research and design.Aiming at the problem of narrow bandwidth of traditional microstrip circular polarization antenna,a broadband circular polarization antenna with wide axis ratio of question mark is proposed.The antenna bandwidth is broadened by opening rectangular ring radiation patch.The circular polarization wave is excited by the ground plane triangle perturbation structure,and the antenna circular polarization characteristics are improved by the re-deformation of the radiation patch.The measured results: the relative impedance bandwidth of the antenna is 137.98%(2.47GHz～13.46GHz),the absolute bandwidth of the axial ratio is 2.57GHz(4.08～6.65GHz),the peak gain is 5.37 d Bi,and the design of broadband circularly polarized antenna is realized.2.Research and design of a multi-antenna multi-frequency circular polarization antenna.Aiming at the problems of low gain of traditional circular polarization receiving antenna and single frequency band of microstrip antenna,a multi-band circular polarization antenna integrating active circuit and multiple antennas is proposed.The antenna amplifies the received small signal by integrating the active amplifier circuit on the PCB board.At the same time,the antenna isolation is effectively improved by adjusting the antenna spacing and arrangement order to eliminate the multi-antenna spatial wave coupling.To solve the problem of limited space of wireless terminal and polarization mismatch of linear polarized antenna,the antenna unit is miniaturized by using high dielectric constant dielectric substrate and curved flow technology to realize miniaturization of the antenna.At the same time,the antenna excites orthogonal electromagnetic wave by A-type single-feed diagonal tangent to realize the left and right rotation circular polarization.The measured results: the antenna reaches S11<-10 d B in each frequency band,the axis ratio<3d B,the passive gain in L-band is more than 2d Bi,the active gain in 3 bands(B1L1,S and B3)more than 10 dBi.