Study On A Cylindrical Rapid Near-field Antenna Measurement Systems

In the near-field antenna measurement, mechanical scanning by a single probe is time-consuming. It is difficult to achieve the purpose of fast antenna testing. So the research on the rapid antenna measurement systems becomes widely prevalent. The near-field measurement systems based on probe array technique can improve efficiency and accuracy of antenna measurement. In this paper, the development of near-field antenna measurement and a brief analysis of fast testing phased array antenna technique based on switch method are introduced. The probe array technique is mainly described. The cylindrical rapid near-field antenna measurement systems is a multi-probe systems composed of a linear array of dual-polarized probes as a receiver, this facility has been designed for1.0GHz to3.0GHz. The dual-polarized probes array and switch array are detected by control software, the signal received by probes array followed by a switch array and power divider into the receiver.Dual-polarized linearly tapered slot antenna as the element of probes array, which is designed by metallic and resistive loading method. A bandwidth ranging from1.16GHz to3.0GHz for VSWR less than2.0is achieved, the relative impedance bandwidth is92%and isolation between ports is less than-22dB. Moreover, the cross-polarization is seen to less than-15dB. On this basis, a linear array of probes with four dual-polarized linearly tapered slot antennas is designed. The probe array has a wide impedance bandwidth from1.05GHz to3.0GHz for VSWR less than2.0and isolation between the same polarization and different polarization is less than20dB. Measured results primarily agree with the simulation theory.In this paper, the main errors of the cylindrical rapid near-field antenna measurements are subdivided into three categories:probe error, truncation error and near-far field transformation error. The probe and antenna under test corrected equation, measurement of the probe coefficient and the theoretical model of truncation error are proposed. The near-far field transformation error is mainly analyzed. Standard horn is used as antenna under test and simulated by FEKO5.3. The far field pattern is obtained. By cylindrical wave expansion method, the far field pattern of the theoretic analysis is gained for the use of cylindrical near-field data. Comparative analysis of simulated and calculated far-field pattern is given.