Research On Key Technologies For Circularly Polarized Antennas And Integrated Antennas

The research content of this paper mainly focuses on two directions:circularly polarized antenna design and millimeter-wave integrated antenna design.Circularly polarized antennas are widely used in wireless communication systems such as satellite communications and radio frequency identification due to their numerous advantages;The millimeter-wave band application is rapidly developed due to its many advantages,such as ample spectrum resources,small antenna area and high gain,and higher spatial resolution.The millimeter-wave applications have been rapidly developed in the fifth generation of mobile communication systems,automotive radars,and military applications.The main work and research contents of this dissertation include the following aspects:1.The theory of designing circularly polarized antennas by conventional sequential rotation technology is further analyzed and studied.Firstly,the array based on sequential rotation technology is analyzed,which contains N radiation elements and these elements are evenly distributed along the z-axis.When the number of elements is more than 3,the feed amplitude of each radiation element is equal,and the phase difference is±（2π/N+2mπ）,where m is an integer greater than or equal to 0,then the antenna will achieve perfect circularly polarized radiation in the z-axis direction,where the polarization orientation in the positive and negative z-axis directions is opposite.Next,the influences of the feeding amplitude and phase errors on the axial ratio of the array are analyzed,and the guidance of optimizing the radiation element is also proposed,that is,the element’s axial ratios should be kept at a low level in a wide frequency band.Finally,a scheme for designing a series-fed dual circularly polarized antenna is proposed.All radiation elements have the identical structure,the series-fed transmission line is evenly distributed,and the overall array structure is symmetrical.By appropriately optimizing four key parameters,the array can achieve circularly polarized radiation with high port isolations,the relationship between the axial ratio and four key parameters of the array is derived and thoroughly discussed.2.Two series-fed circularly polarized antennas are designed.Firstly,a dual-band series-fed slot helix antenna is designed as an improved dual-band quadrifilar helix antenna.The antenna uses dual-band slots as the radiation elements,and the series-fed microstrip line acts as a feeding network which is terminated with an absorber.All the radiation elements and the feeding network are printed on a single layer substrate,which has a simple structure and low processing cost.Then a wideband traveling-wave circularly polarized antenna printed on single-layer PCB for millimeter-wave applications is presented.The antenna uses a curved microstrip line as the radiation element,and the substrate integrated waveguide serves as the connecting adjacent radiation elements.A new approach to increase the axial ratio bandwidth is proposed in this paper.A cross-polarization offset subarray is set at the edge of the array and has different polarization directions and out-of-phase feeding compared to other radiation subarrays.The cross-polarization components of the array will be offset.3.Two series-fed dual circularly polarized antennas are designed.A dual circularly polarized series-fed array based on the sequential rotation technique with uniform radiation elements is designed as a verification of the theory mentioned above.The radiation elements and feeding network used in the array are uniform,which leads to the possibility of dual circularly polarized radiation by series-fed SR arrays.The proposed series-fed array has comparable performance but simpler structures and easier design process compared with other parallel-fed arrays.Then a low-cost,single-layer,dual circularly polarized series-fed antenna based on the sequential rotation technique for millimeter-wave applications is presented.The series-fed working form endows the proposed antenna with more compact structure and lower ohmic,dielectric losses caused by the feeding network compared with parallel-fed antennas.The curved microstrip transmission lines are adopted as radiation elements;therefore,the whole antenna can be etched on a single-layer laminate using standard printed circuit board technology,which has high precision and low cost.4.Two millimeter-wave integrated antennas are designed.Firstly,a low-cost wideband circularly polarized antenna array that is excited by a substrate integrated coaxial line with mature and stable processing technology is designed for millimeter-wave applications.The proposed 4×4 antenna array acquires high-purity CP radiation through sequential-rotation techniques.The antenna comprises two substrate layers that are bonded by bonding film.The feeding network and radiation elements are directly connected in the same plane instead of to a coupling structure between different layers given that the widths of the SICL are considerably smaller than those of substrate integrated waveguides.This design scheme reduces the antenna cost and improves machining accuracy.Then,a dual-polarized series-fed array antenna with 30°beam-pointing for millimeter-wave applications is presented.The45°and-45°polarized subarrays share the aperture in the shape of interdigital.The spacing between subarrays with the same polarization orientation is set to 0.56λ₀ through the using of narrower T-Type folded substrate integrated waveguide instead of substrate integrated waveguide.The substrate integrated coaxial line is adopted to design the array feeding network.a 4×6（single polarization）dual-polarized array antenna operating at 28 GHz with30°beam-pointing is fabricated.