Design And Research Of Single-fed Circularly Polarized Antenna

With the rapid development of radio frequency and microwave integrated circuit technology,wireless communication systems have been widely used in military and civil fields.As the core component of wireless communication,antennas have attracted more and more attention.Linear polarization(LP)antenna is easily affected by signal fading and multipath interference,which leads to signal distortion and affects signal quality.At the same time,when transmitting and receiving electromagnetic waves,the linear polarization antenna must strictly comply with the polarization uniformity,otherwise the signal strength will be reduced due to polarization loss.Circular polarization(CP)antenna can receive electromagnetic waves from any direction,improve signal reception and transmission in complex environments,reduce fading caused by environmental changes,and circular polarization antenna is less affected by polarization mismatch.Single-fed circularly polarized antenna has obvious advantages due to its simple structure,strong resistance to multipath interference and improved channel capacity.For this reason,three new designs of single-feed circularly polarized antenna are studied in this thesis,and experimental verification is completed.It mainly includes the following three aspects:Firstly,a three-dimensional compact propeller circularly polarized antenna loaded by an inverted L-shaped slot is designed by using coaxial back-feeding.The antenna structure has small size,single-fed and half-plane radiation mode.The antenna consists of four alternately welded radiation elements and a disk-shaped reflector.Each radiation element is formed by a rectangular microstrip radiation plate and a trapezoidal microstrip transmission line.The measurement results show that the 10-d B impedance bandwidth is 66.3%(4.4～8.94GHz),and the 3-d B axial ratio bandwidth is 2.2%(6.44～6.58GHz).The radiation characteristics in the xoz plane and the yoz plane are close to that in the half-space.The peak gain of the antenna in the operating band is between 3.04 d Bi and 3.22 d Bi.Secondly,a planar microstrip ultra-wideband(UWB)single-fed circularly polarized antenna loaded with a annular slot is proposed and designed by using microstrip line side-feed.The circularly polarized radiation and the broadening of the axial ratio bandwidth are realized by loading annular slot on the radiation patch,asymmetric inverted L-shaped microstrip lines and cutting the radiation patch by a quarter circle.The simulation and measurement results show that the 10-d B impedance bandwidth of the antenna is 56.2%(4.52～8.06GHz),the 3-d B axial ratio bandwidth reaches 21.25%(5.9～7.3GHz),and the peak gain within the 3-d B axial ratio bandwidth is between 3.74 d Bi and 4.59 d Bi.Finally,a broadband circularly polarized printed monopole antenna is proposed and designed by using the coplanar waveguide(CPW)feed.The antenna consists of a quarter circular radiation monopole,a coupled circular patch,a curved L-shaped microstrip short line and an asymmetric ground.L-shaped microstrip short line,asymmetric ground structure and circular coupling patch jointly improve the impedance bandwidth and axis ratio bandwidth,and the antenna can generate right/left circular polarization waves in the ±z axis direction.The measurement results show that the 10-d B impedance bandwidth is 76.9%(6.05～13.62GHz),the3-d B axial ratio bandwidth is 39.8%(6.05～9.06GHz),and the peak gain within the 3-d B bandwidth is between 0.46 and 3.28 d Bi.The three circularly polarized antennas proposed in this thesis all adopt the structure of single feed,and have the characteristics of compact structure,wide axis ratio and dual-polarized radiation respectively.The simulation and test results are consistent,and the research results can be applied to wireless sensors,wireless monitoring and other devices.