| Nowadays,satellite navigation system is very widely used in military and civil applications,since all-weather and global high-efficiency real-time navigation services are provided for land,sea and air fields.However,the intensity of satellite signal is too weak when it's reaching the ground,so that it is easily to be interfered by all kinds of intentional or unintentional interferences which cause the receiver to stop working.Therefore,the research of anti-jamming technology for satellite navigation system is an effective way to improve its practicability.Among the anti-jamming technologies,adaptive spatial filtering technology adopts zeroing response of the array antenna to suppress incoming jamming signals which is an effectively way to improve the anti-jamming ability of the receiver.In this paper,adaptive spatial anti-jamming technology is studied and applied to satellite navigation array antenna.The specific contents are:Firstly,the adaptive spatial anti-jamming technology is studied which contains DOA estimation and adaptive beamforming technology.By comparing the characteristics of common DOA estimation technology and the DOA estimation based on subspace,the MUSIC algorithm based on subspace is decided to be used to estimate the direction of interference signals finally.Then adaptive beamforming algorithms are studied based on corresponding criterions of spatial filtering.The SMI algorithm is as the final method to form nulls at the interference directions so as to achieve the aim of interference suppression.Secondly,the theoretical basis of adaptive antenna array for satellite navigation is studied.A miniature circularly polarized microstrip antenna working in B3 band is designed.A RHCP characteristic is achieved through a single point feed and geometric perturbation and the miniaturization characteristic is realized by using high dielectric constant substrate.The overall size of the antenna is 0.18?0×0.18?0×0.017?0 and the axial ratio of the working frequency is less than 3d B while the gain can obtain 5.2d Bic.Adapting to multi system compatibility,a wideband satellite navigation circular polarization antenna is designed which working frequency is from 1164MHz to 1616MHz.The antenna is mainly composed of a pair of square dipole radiation patches with arc grooves and a wideband feed network.Within it's working frequency,the VSWR of the antenna is less than 1.5 and AR<2,Gain>5.8d Bic.At last,two 6-element arrays based on above antenna are designed,respectively.And the beam scanning characteristics of the corresponding array are analyzed.Finally,the decoupling method based on element pattern reconstruction is studied to solve the problem of poor anti-jamming effect caused by mutual coupling effect between antenna elements.The problem is manifested in the inaccurate direction estimation of interference signals and the null adjustment of pattern.By this method of decoupling,the direction of interference signal can be accurately detected based on MUSIC algorithm.Accurate nulls with a depth greater than 100d B in the directions of interferences can be formed based on the beamforming technology of SMI algorithm.At the same time,a maximum value in the expected direction is formed.The ability of the anti-jamming of the actual satellite navigation antenna is improved extremely.What's more,in order to meet the requirement of the wideband satellite navigation antenna can achieve the ability of anti-jamming in whole working frequency band,electromagnetic field information at any frequency within working frequency band are obtained by Hermite interpolation method. |
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