Research On Multi-band And Circular Polarization Antenna Based On Miniaturized Substrate Integrated Waveguide

With the updating of communication equipment and the development of communication technology,the requirements for antenna performance in communication systems are more diversified.Substrate integrated waveguide(SIW)has the characteristics of low loss,low cost,easy to fabrication,and maintains most of the excellent characteristics of metal waveguides.Therefore,the designs which using SIW technique have considerable application prospects and development space in communication systems.Besides,multi-frequency antennas can meet the needs of multi-band communication and circular polarization antennas can reduce the effects of polarization mismatch,they are also widely used in various communication devices.Multi-band and circular polarization antennas based on SIW and its miniaturized structure are studied in this thesis.The main contents of our research are shown as follows:1.A diplex antenna with a common radiator and high isolation is proposed.When the SIW cavity is excited by different ports,the hybrid modes with different resonant frequencies are forming in this cavity,then the diplex antenna is achieved.The antenna exhibits independent frequency tunability at the two resonant frequencies,and the isolation between the two ports is better than 21d B.After that,a dual-band antenna with independent frequency tunability and low cross-polarization level is proposed.The half-mode substrate integrated waveguide(HMSIW)technique is employed to reduce the size of the SIW cavity.The cavity mode is disturbed by etching a slot parallel to the cavity radiation side,then the dual band antenna is realized.Then,the cross-polarization level of the two operating bands is less than-23d B.Finally,a tri-band antenna is proposed.By etching two slots with different length on the HMSIW cavity,the tri-band is obtained.Similar to the dual-band antenna,the tri-band antenna also exhibits independent frequency tunability with cross-polarization level less than-20d B.2.A broadband circularly polarized antenna with high gain is presented.A combination of three Wilkinson power dividers is used to design a sequential phase feed network,and the four HMSIW antenna elements are excited by the probes which connected with the feed network to form circularly polarized radiation.Besides,another mode is formed by introducing a shorted parasitic patch to expand the gain bandwidth.A radiation null is introduced by the coupling between the two modes to improve the suppression of the out-of-bands.By changing the arrangement of antenna elements and parasitic patches,the gain of the antenna is further improved and the side lobe level is decreased.Finally,the-10d B impedance bandwidth of the antenna is 41.5%,the 3d B axial ratio bandwidth is 20.3%,and the gain of 10.34d Bi and 9.91d Bi are obtained at the resonating frequency of the half-mode cavity and parasitic patch,respectively.3.A single-layer broadband high-gain circularly polarized antenna is proposed.The sequential phase feed network and the HMSIW antenna elements are integrated on the same layer to simplify the complexity of the antenna.The-10d B impedance bandwidth of the antenna are 36.1%,and the peak gain are 8.9d Bi under the low profile of 0.008?₀(?₀ is the free space wavelength corresponding to the center frequency).After that,a low-profile high-gain circularly polarized antenna with simplified feeding network is proposed.The sequential phase feed network is replaced by a rectangular patch which resonating at its higher-order modes(TM₁₂₀ mode and TM₂₁₀ mode)to feed the four quarter-mode substrate integrated waveguide(QMSIW)cavities.Because the radiation field of the QMSIW cavities and the rectangular patch are superimposed in the same direction in the far field,the gain of the antenna reaches up to13.1d Bi.Finally,by removing part of the metallic vias of the QMSIW cavities,part of the energy is transmitted to the parasitic patches of the QMSIW cavities through the coupling window formed between the metallic vias,then a gain of 14.1d Bi is achieved in the antenna.