Study Of Monostatic Near-field Scattering Measurement Method Of Antenna

Antenna measurement is important for antenna design,antenna manufacture and antenna adjustment.In this field,traditional far-field measurement method is strict for measurement environment,measurement weather and other requirements.Compared with the far-field measurement,near-field measurement can be performed indoor,so it is less affected by measurement environment and has good property of keeping secret.Therefore,near-field measurement method has become an important method in the research of determining scattering characteristics about antenna at home and abroad.In this thesis,we choose near-field scattering measurement method by the research on antenna scattering theory and near-field measurement technique,the three-dimensional algorithm and descending dimensional algorithm on near-field to far-field transformation are derived and optimized to improve the calculation efficiency.The scattered near-field data can be obtained with the near-field scanning of target and antenna under test.By comparing the RCS obtained by near-field to far-field transformation algorithm with the actual RCS as the ideal plane wave incidents,the correctness of the near-field to far-field transformation algorithm is proved.The specific content as follows:Firstly,the field region distrition of antenna is introduced and the advantages and disadvantages of several different kinds of near-field measurements,near-field scattering measurement method are analyzed.In the meantime,the three-dimensional algorithm and descending dimensional algorithm of the near-field to far-field transformation is derived and optimized from mathematical relationship.Secondly,with the cylindrical conductor as target under test,the monostatic near-field scattering measurement method is studied by computer simulation with the electric dipole as the probe.By comparing the RCS obtained by near-field to far-field transformation algorithm based on spherical scan is adopted with the actual RCS,the correctness and validity of the descending dimensional transformation algorithm.In this thesis,we give the effect of near-field measurement distance on the precision of descending dimensional algorithm and compare the computation time using fast algorithm or not.Next,the cylindrical conductor and the pyramid horn antenna are taken as the targets under test respectively,the monostatic scattering measurement method is studied by computer simulation by using an electric dipole as the probe.By comparing the RCS obtained by near-field to far-field transformation algorithm with the actual RCS,the correctness and validity of the three-dimensional algorithm is proved.For the three-dimensional algorithm,the associated Lagendre function and integral term are dealt with to optimize the algorithm and improve the calculation efficiency.By comparing the computation time using fast algorithm or not,the validity of the fast algorithm to accelerate the computation speed is proved.Finally,the error sources in the monostatic near-field scattering measurement method are analyzed and compensated.The precision of the measurement is further improved.