Research On Compensation Technology And Error Analysis Of Planar Near-field Measurement Prob

Antenna measurement is a direct method to test the antenna performance,and the accuracy of results is of vital importance to antenna design.Therefore,the accuracy is an important index of antenna measurement.In the planar near field measurement system,the influence of measurement probes cannot be ignored,and the compensation algorithm for the probes is crucial to improve the test accuracy.Thus,this thesis is to study the near-field far-field transformation based on the planar wave spectrum method and equivalent magnetic current method.At the same time,the corresponding probe compensation algorithm is proposed to correct the near-field measurement results in order to improve the measurement accuracy,with the probe pattern obtained by theory,simulation and measurement.Finally,the measurement error is analyzed.The main research is as follows:1.Near-field far-field transformation including the planar wave spectrum method and equivalent magnetic current method was researched.And probe compensation algorithms were also studied.Three probe compensation algorithms were mainly studied:（1）The relationship between the plane wave spectrum and the antenna far field pattern was established,and the mutual coupling equations between the probe and the antenna under test was constructed based on the plane wave reception coefficient of the probe.Thus,the antenna pattern without the influence of the probe was obtained.（2）With the three-dimensional probe radiation pattern（the radiation reception performance coefficient matrix）fitted from the E and H plane patterns of the probe,an approximate near-field compensation algorithm was proposed to correct the near-field data,and the compensated far-field antenna pattern was calculated using the equivalent magnetic current algorithm.（3）A near-field electric field matrix equation containing the influence of the probe was established based on the plane wave theory,reciprocity theorem,and stationary phase method.The near-field electric field without the influence of the probe was then calculated,and the compensated antenna pattern was computed using the equivalent magnetic current algorithm.2.Probe compensation experiments were carried out.Horn antenna was selected as the device under test（DUT）,and the electric field distribution was measured in the near field 3λapart from the DUT aperture.The following experimental researches were done:（1）Antenna patterns with and without compensation was obtained with plane wave expansion algorithm and three probe compensation methods.After comparison with the results from compact range measurement,it was found that E plane pattern without compensation was in good agreement with the measured one,while the H plane pattern had large errors in side lobes.Three compensation methods all helped improve the accuracy of the results,and the error of the 2^ndsidelobe reduced 3-db B.The compensation results were best with the simulation probe pattern,which increased the agreement area of the antenna pattern from±40°to±70°.（2）Antenna patterns with and without compensation was obtained with equivalent magnetic current algorithm and four probe compensation methods.After comparison with the results from compact range measurement,it showed that four compensation methods all helped improve the accuracy of the results greatly.The antenna pattern has higher accuracy with the probe compensation by simulation and plane wave method,which increased the agreement area of the antenna pattern from±30°to±70°.3.Error analysis of measurement were researched.In order to solve the accuracy error caused by different influencing factors in planar near-field measurement,the measurement error uncertainty was first defined,and four possible error sources during the measurement process were chosen for quantitative research.the uncertainty of the four parameters were analyzed,and corresponding experimental researches were carried out.The experimental results showed that the uncertainty of the four error sources was less than 0.1 in a suitable experimental environment,and only the second side lobe portion of the antenna pattern was influenced.Therefore,under the reasonable experimental parameters conditions,the experimental results have high reliability.