Study On Planar Bi-sensing Circularly Polarized Antennas

In recent years,the gain enhancement technology of endfire circularly polarized antennas has received more and more attentions and developments,which are limited by the more complex configurations,larger electrical sizes and higher antenna heights.Therefore,it is essentially important and tough to realize a planar backfire circularly polarized antenna or planar bi-sensing circularly polarized antenna with its beam in parallel to its plane,in order to further design a gain-enhanced planar endfire circularly polarized antenna.This thesis aims to achieve a planar bi-sensing circularly polarized antenna with the above characteristics,and attempts a new method of generating planar bi-sending circularly polarized antenna with its beam in parallel to its plane.The main content of this thesis includes:1.In order to design a novel planar bi-sensing circularly polarized antenna,design guidelines of a circular sector compact planar quasi-isotropic antenna are presented.General relationship between the non-uniformity and flared angle is deduced at first.Then,it is employed to determine the usable flared angle range for non-uniformity is less than 3dB.Based upon the design guidelines,a compact planar quasi-isotropic antenna is conceptually designed and numerically studied.It is seen a circular sector magnetic dipole antenna with flared angle of 300° can exhibit both quasi-isotropic radiation characteristic and compact size.2.Design approach to a planar bi-sensing circularly polarized antenna is presented.The antenna is composed of a circular sector magnetic dipole and two concentric annular electric dipoles.At first,the flared angle,radius of the circular sector magnetic dipole and the feed positions of electric dipole are determined by the phase difference condition for bi-sensing circularly polarized radiations.Then,the arc length of concentric annular electric dipoles is determined.Finally,a concentric annular parasitic element is properly employed to compensate the phase and amplitude difference.In these ways,bi-sensing circularly polarized antenna with main beam in parallel to its plane can be realized by using a simple planar configuration with only a few design parameters.As experimentally validated,the proposed antenna exhibits a nearly perfect bi-sensing circularly polarized characteristic at 2.50 GHz band.3.On the basis of planar bi-sensing circular polarization,the endfire and backfire circularly polarized antennas are further realized.An endfire circularly polarized antenna with gain enhancement,increased circular polarization range,and broadened beam width is achieved by adding a 3-D reflector.In the backfire direction,two pairs of directors are added to the planar uncompensated bi-sensing circularly polarized antenna to obtain a backfire circularly polarized antenna,which is fabricated and measured to verify the feasibility and effectiveness of the method.