Research On The End-fire Circularly Polarized Antenna

As an important device of sending and receiving signals,antenna is widely used in wireless systems,the performance of the system is related to the quality of the antenna.The end-fire antenna is always used in wireless systems such as radar and long-distance communication with the advantages of high gain,easy conformal shape,small volume and so on.The electromagnetic wave of the circularly polarized antenna can be decomposed into two linearly polarized polarization waves,which can receive arbitrary linearly polarized waves,and commonly used in systems such as electronic countermeasures.The common end-fire antennas are mostly linearly polarized antennas.Combined with the basic principle of circular polarization,the new structure is introduced to provide the linear polarization in the orthogonal direction.This paper presents the research of end-fire circularly polarized antenna.The scope of application of this antenna is more extensive,the application is also more flexible.In this paper,three kinds of planar end-fire circularly polarized antennas are proposed,and the idea and method of realizing circularly polarized radiation of end-fire antenna are discussed.The main contents and research results are as follows:Firstly,a new multi-patch-oriented microstrip circularly polarized Yagi antenna is designed in combination with Yagi end-emitting antenna and microstrip patch antenna.The antenna adopts the method of single feed point and perturbation to realize the circularly polarized radiation of the excitation patch,and the mutual coupling between the patches is used to direct the energy to the end-shot direction to achieve the circular polarization radiation of the Yagi antenna.The center frequency of the antenna is 5.8GHz,the relative bandwidth of the return loss more than 10 dB is about 300 MHz,the bandwidth of 3dB axial ratio(AR)is 100 MHz,the gain is up to 2.5dB,and the circular polarization characteristic is better.Secondly,using the substrate integrated waveguide(SIW)and H-plane horn,this paper proposes a plane end-fire circularly polarized antenna working in the Ku-band center frequency of 15 GHz.The circularly polarized radiation unit is made up of H-plane horn and Yagi oscillator,where the H-plane horn provides vertical line polarization,and the Yagi oscillator offers horizontal line polarization,and the transition length of the aperture of the horn to the Yagi oscillator achieves 90 ° phase delay.The antenna has a 16% impedance bandwidth,the AR is less than 3 dB from 14.4 to 15.2 GHz,and the gain is 5.5 dBi,which realizes the circularly polarized radiation in the end direction.Finally,in order to improve the gain of the antenna,a plane end-fire circularly polarized antenna is fabricated with a center frequency of 35 GHz.Similarly,the vertical polarization wave is generated based on the SIW H-plane horn,except that the dipole subarray is introduced to produce a horizontally polarized wave.The dipole array is connected to the upper and lower metal sfaces of the horn,which is sercices as reflection surfaces of the dipole arrays to obtain directional radiation.The antenna is fed by gradient waveguide,the measured results are in good agreement with the simulated results,which show that the impedance bandwidth of the antenna is 22.9%,the AR bandwidth is 14.3%,the maximum of gain is 10.7dB.The antenna is a left-handed circularly polarized antenna with the direction of the end-beam is parallel with the antenna plane.The design of the antenna,especially the last two antennas,expatiates the idea of designing a circularly polarized antenna in this paper,that is: in the basis of the end-fire vibrator,introducing a new structure to provide linear polarization in the orthogonal direction to realize circularly polarized radiation.The measured results and the simulated results prove the feasibility of the design.