Research On High Performance Antenna Based On Substrate Integrated Waveguide Technology

Nowadays,wireless communication systems are developing rapidly in the direction of miniaturization,highly integrated,broadband and high-speed,and the demand for high-performance antenna is also increasing.Substrate integrated waveguide(SIW)antennas have been widely used in microwave and millimeter-wave communication systems due to their advantages of low loss,high efficiency,light weight and easy integration with other planar circuits.In this dissertation,the research status of various high-performance SIW antennas is summarized systematically,and some basic theories of SIW technology are introduced briefly.Finally,the relevant design methods of high-performance SIW antennas are studied deeply.In order to solve the technical difficulty faced in the design process of SIW antennas with different performance,such as high gain,high aperture efficiency,low cross-polarization wideband and miniaturization,some innovative design ideas and technical means are proposed.The main contents and contributions of this dissertation are as follows:(1)Generally,the aperture efficiency of traditional single layer monopulse antenna using SIW technology is relatively low.To address this problem,a X-band single layer SIW slot array monopulse antenna with high gain and high aperture efficiency is studied and designed.Firstly,the E-field distribution of high order modes of SIW cavities is analyzed.And then,a novel feeding method for SIW monopulse antenna is proposed.When the electromagnetic energy between the feeding cavity and the radiation cavity is coupled through two opened windows,the single layer structure can be realized.The monopulse comparator of the proposed antenna consists only of a square SIW cavity.Sum beam and difference beam can be realized when resonant modes of the square SIW feeding cavity are high order TE₁₂₀ mode and TE₂₁₀ mode respectively.Because of the orthogonality between the two high order modes,good port isolation is obtained between the sum and difference ports.In addition,the area occupied by the monopulse comparator is greatly reduced by this novel feeding method,thus the aperture efficiency of the antenna is improved effectively.(2)To meet the requirement of broadband and high gain,a SIW planar slot array antenna with wideband,high gain and low cross-polarization is designed.The linear array element of the proposed antenna array has two high order quasi-TE₁₅₀ modes with similar frequencies which helps to improve the bandwidth.Besides,the adjacent liner array elements are arranged alternately so that their cross-polarized radiation can be cancelled out.And this is also conductive to the implementation of a compact feeding network.The proposed antenna obtained a relative impedance bandwidth of 4.4%(9.9-10.34 GHz)and its cross-polarization is lower than-52.1 d B within the operating band.(3)In terms of miniaturization and low profile,three high performance antennas based on fractional SIW cavity are studied and designed.Fisrstly,a wideband linearly polarized antenna utilizing a triangular half-mode substrate integrated waveguide(HMSIW)cavity is proposed.The radiation characteristics of the fundamental mode(HM-TE₁₁₀)and the high order mode(HM-TE₂₂₀)of the HMSIW cavity are similar.Therefore,bandwidth can be improved by merging these two modes.The measured relative impedance bandwidth of the proposed antenna is about 5.1%and its maximum gain is 6.1 d Bi within the operating band.The proposed antenna has high performance of low profile,small size,broadband and low cross-polarization.Then,a differential feeding CP antenna consisting of two triangular quarter-mode substrate integrated waveguide(QMSIW)cavities is designed.The triangular QMSIW cavity under the fundamental mode(QM-TE₁₁₀)and the high order mode(QM-TE₂₂₀)can radiate electromagnetic wave with orthogonal polarization.Thus,CP radiation can be obtained when metallized vias are added to merge the two orthogonal modes.However,a single QMSIW cavity has the disadvantages of high cross-polarization and low gain.For better performance,a differential feeding CP antenna array is designed by arranging two CP antenna elements180°rotated.Finally,a single layer and high gain CP antenna based on cascaded QMSIW cavities array is proposed.The proposed antenna consists of a central quasi-squared microstrip patch and four QMSIW cavities which are connected at each corner of the patch.Due to the proper asymmetries of the structure,two orthogonal high-order modes can be excited by a single feeding port.Therefore,high gain CP radiation can be realized.The measured results show that the maximum gain of the proposed antenna is 10.4 d Bi.