Study On Design And Compensation Theory Of Wideband Dual-polarized Probe In Planar Near-field Scanning

Near-field scanning technology is one of the important methods of antenna measurement.As an indispensable part of it,the performance of probe has a great effect on the accuracy and efficiency of near-field antenna measurement.In near-field antenna measurement,if the available bandwidth of probe exceeds that of the antenna under test(AUT),there will be no need to replace probe in measurement process,which makes the installation and calibration of probe only need once,saving measurement time.If probe has dual polarization,it can measure two orthogonal field components simultaneously without the need for a second scan through mechanical rotating,further reducing measurement time and saving expensive rotating positioner.For the narrow frequency band of common rectangular waveguide probe and the need for two scans,this paper mainly studies the design and compensation theory of wideband dual-polarized probe in planar near-field scanning.Firstly,a L-shaped dual-polarized balanced Vivaldi probe(BVA)is designed for the actual needs of wideband dual-polarized probe in near-field antenna measurement.By loading slots and resistors on the radiation wall,BVA is miniaturized.The total size of BVA is 113mm×105.8 mm×105.8 mm,in 0.6-6 GHz the voltage standing-wave ratio(VSWR)of two ports are less than 2,the isolation between two ports is greater than 25 dB,the E plane and H plane pattern are good,the maximum gain is 7dB,the cross polarization is less than-15dB.Secondly,an open-boundary quad-ridged circular horn probe(QRHA)is designed in order to expand the measurement frequency band.By adding Bessel curve at the end of exponential ridge curve,the main lobe split of high frequency pattern is improved and the QRHA size is reduced.The total size of QRHA is 115 mm×110 mm×110 mm,in 2-20GHz the VSWR of two ports are less than 2,the isolation between two ports is greater than40 dB,the E-plane and H-plane 3dB beam width are greater than 20~?,the gain is 3-15 dB,the cross-polarization in the maximum radiation direction is less than-25 dB.Finally,the simulation results of planar near-field to far-field transformation without or with probe compensation are given respectively using pyramidal horn antenna as AUT.The non-probe compensation is validated by theoretical formula method and HFSS simulation method,and the far-field pattern obtained by transformation is in good agreement with the theoretical pattern in the range-60~????6 0~?.In addition,the far-field pattern of rectangular waveguide probe is represented by E-plane electric field method,edge current approximation method and HFSS simulation method respectively.The comparison results of different compensation methods for rectangular waveguide probe are given through measured data,which verifies the effectiveness of HFSS simulation method compensation,and the compensation theory of wideband dual-polarized probe is studied.