NIM球面近场法天线校准装置的测量不确定度评定

介绍了中国计量科学研究院（NIM）开发的一套精密球面近场扫描法天线校准装置(400 MHz～110 GHz)在测量天线归一化方向图（限于幅度）时的不确定度评定。以“自我比较法”为基础,简介了探头、安装对准、数据采样和射频系统等引入的18个不确定度分量的评定结果,重点针对天线暗室反射引入的不确定度不易评估的难题,基于射线追踪法提出了一种分析、测量和计算相结合的“干扰法”。评估结果表明该套近场系统在-40 dB副瓣电平内,重复性优于0.1 dB (26 GHz)、在忽略探头极化误差时的扩展不确定度优于2.7 dB。最后分析了球面近场天线测量的不确定度特点。

Uncertainty Evaluation of NIM Spherical Near-field Antenna Calibration Facility

Some research is made for the uncertainty of normalized antenna radiation pattern (only amplitude) from NIM precise spherical near-field (SNF) antenna measurement facility (400 MHz to 110 GHz). There are 18 uncertainty items from probe, mounting, data sampling and radio-frequency system are introduced in brief, based on "self-comparison approach". A detail "perturbation method" is proposed to evaluate the scattering from the anechoic chamber based on the ray-tracing method; it is known that sometimes it is impossible to move the spherical system in the anechoic chamber to evaluate the scattering from the absorber. The evaluation results show that for NIM’s SNF facility, when the side lobe up to -40 dB, the repeatability is less than 0.1 dB (26GHz), and the expanded uncertainty for a normalized radiation pattern (amplitude) is 2.7 dB when ignoring the cross-polarization of the probe. Finally, the uncertainty characteristics of a SNF facility is summarized.