Substrate Integrated Circularly Polarized Cavity-backed Antenna

A circularly polarized antenna is widely used in various wireless communication systems, as it has a number of advantages compared with linearly polarized antenna. And circularly polarized cavity-backed antenna has many excellent properties, such as: stable radiation pattern, high gain and small backward radiation. The circularly polarized cavity-backed antenna and the feeding network can be integrated in the dielectric plate by using the multilayer printed circuit board technology, thereby the antenna array has been effectively simplified to meet the modern communication system demands of miniaturization and integration. In this paper, the substrate integrated circularly polarized cavity-backed antenna has been studied in depth, and three circularly polarized cavity-backed antenna units and arraies have been designed based on different principles to produce circular polarization.In chapter 1, the research background and significance of this paper are introduced. Then, the origins, development and research status of the traditional circularly polarized cavity-backed antennas and the substrate integrated cavity-backed antennas are reviewed. Several typical circular polarized cavity-backed antennas have been presented. Finally, the main content and structure of this dissertation are outlined.In chapter 2, the basic designing principle of the cavity-backed antenna is described, and the mode distribution in the cavity by using the opened cavity model is analyzed. Then a brief introduction of the field distribution of the mode in the different shapes of waveguides, such as square waveguide, circular waveguide and elliptical waveguide, is given, according to the shape of the cavity in this paper. Finally, the equivalence principle of the substrate integrated waveguide and the designing principle of the waveguide slot antenna are introduced.In chapter 3, a circularly polarizated cavity-backed antenna element with a rotary ellipse cavity, which is fed by a SIW slot, has been presented. The circular polarization has been achieved by excitation of two orthogonal modes in the cavity. For the shortcoming of narrow axial ratio bandwidth of the antenna unit, a novel substrate integrated waveguide power divider has been designed. A 4?4 circularly polarized antenna array is designed by combining the circularly polarized antenna elements and the power divider. The results show that the axial ratio bandwidth has been effectively broadend to 34.4%.In chapter 4, a circularly polarized cavity-backed antenna element with a pair of triangular loaded patch is presented, and the circular polarization has been achieved by the two orthogonal modes on the patches excited by the SIW slot. A 4?4 circularly polarized antenna array is designed by combination of elements and the substrate integrated waveguide power divider as the same of the one introduced in chapter 3. The results show that, compared with the circularly polarized antenna array introduced in chapter 3, the array with loaded patch has broadend the impendence bandwidth with 2.4%, and the gain has been improved by 1d Bi. Finally, two kinds of improvements to the shape of the cavity have been introduced to increase the aperture efficiency of the antenna, and the aperture efficiency of the antena array has been increased with 1.6% and 3.8%, respectively.In chapter 5, a circularly polarized cavity-backed antenna element with an S-shape loaded patch, which is worked at 60 GHz, has been proposed. And the circular polarization is achieved by combination of the radiation fields of the slot and the patch. A 4?4 circularly polarized antenna array is also designed by combination of elements and the substrate integrated waveguide power divider as the same of the one introduced in Chapter 3. Simulation results show that the impedance bandwidth of the antenna is 9.3% and the axial ratio bandwidth is 8.6%, which has covered the bandwidth of the 60 GHz wireless personal area network application.In chapter 6, the contents of this paper and the prospects of the future works are summarized.