Research On Circularly Polarized SIW Slot Antennas

In satellite communication systems,antennas are demanded to have a high gain,be insensitive to antenna locations,be able to eliminate the signal Faraday rotation effect caused by the ionosphere,and have strong anti-interference ability.Therefore,the circularly polarized(CP)radiation and high gain properties become very important for the satellite communication Antennas.Meanwhile,the substrate integrated waveguide(SIW)antennas have many advantages such as high gain,high efficiency,good applicability for high frequency design,low profile and low fabrication cost.In this thesis,the design of CP array based SIW structures is investigated,and two CP SIW slot antenna arrays are proposed for satellite communication application.The main research is given as follows.Firstly,the research status of CP SIW slot antennas is reviewed.The influence of different SIW width and thickness values on the antenna performance is analyzed.The transitions between SIW and microstrip-line and waveguide are discussed.Furthermore,SIW slot arrays with different layouts are researched according to the distinctive structure property of SIW.Secondly,a Ka-band SIW-fed CP patch array antenna is designed.The CP element is implemented by loading a pair of split truncated CP patches over the longitudinal slots etched on the upper metal layer of the SIW.Then,a 1×8 linear array is designed based on the traditional longitude waveguide slot array design method.Simulated results show that the impedance bandwidth of the linear array is 3.1%,the axial bandwidth is 2.3%,the gain is 16.0dB,the side-lobe level is about-14dB,and cross polarization isolation is 24dB.Thirdly,a dual-band dual-CP shared-aperture antenna array is proposed by loading a cavity-backed cross-slot antenna over the longitudinal slots on the SIW upper layer.The longitudinal slots are etched to couple energy to array from SIW.The cavity-backed cross-slot antenna is designed to achieve CP radiation.The radiation unit has good isolation characteristics,which is desirable to implement a dual-band shared-aperture array with two frequencies close to each other.Two independent 4×8 planar arrays fed through serial waveguide power dividers are designed at 8.2GHz and 8.6GHz,respectively.Then the dual-band dual-CP shared-aperture array is developed by integrating two 4×8 planar arrays together with an interdigital layout.Measured results show that the impedance bandwidths of 1.3%and 2.8%,the frequency isolations of 40dB and 37dB,the axial bandwidths of 2%and 2.3%,and the gain of 19.5dB and 19.3 dB are obtained at two operating frequencies,respectively.In this thesis,two kinds of antennas are designed to improve the traditional waveguide slot antenna to SIW slot antenna array.The circularly polarized radiation elements are loaded over the longitudinal slots etched on the top surface of the SIW.Those novel SIW antennas not only have the advantages of high gain and high efficiency,but also are easy to achieve circular polarization design.Furthermore,it is very convenient to expand the arrays to implement the high-gain larger arrays.The designs in this thesis have good application prospects due to their compact structure,low profile,easy fabrication with PCB technology,.