基于射频相位的两步测距法

针对多径传播造成基于射频信号相位信息测距不准确问题,提出了一种基于双标签的两步测距法。每一待定位目标上附着两个标签。在单频副载波调幅调制方式下,首先,提取载波信号的卷叠相位信息,计算标签在载波半波长范围内与阅读器的距离值,得到细测距估计值;然后,提取副载波信号的展开相位信息,根据展开相位估计标签与阅读器相距距离中包含的载波半波长的整倍数;其次,计算两个标签对应整倍数的平均值,将该平均值倍的载波半波长距离作为两个标签与阅读器之间距离的粗测距估计值;最后,将粗测距与细测距的估计值相叠加得到双标签最终的测距估计值。另外,为了降低硬件设施成本,提出了基于单阅读器和双标签的几何定位方法。仿真实验结果表明,在复杂多径传播环境中,与直接基于副载波信号相位信息测距相比,基于双标签的两步测距法平均测距误差约降低了35%,最终平均定位误差约为0.43 m,最大误差约为1 m,有效提高了相位法在定位技术中的精度,并降低了硬件成本。

Radio phase-based two-step ranging approach

Concerning the ranging inaccuracy problem based on radio signal phase information under multi-path environments, a two-step ranging approach based on double tags was proposed. Each target was attached with double tags. Through single frequency subcarrier amplitude modulation, firstly, the wrapped phase information of carrier signal was extracted, the distance between reader and tag within half wavelength of carrier signal was calculated and fine ranging estimation value was achieved. Secondly, the unwrapped phase information of subcarrier signal was extracted, and the integral multiple of half wavelength within the distance of reader and tag was calculated. Thirdly, the average multiple was calculated between double tags, the distance of average multiple of half wavelength was used as coarse ranging value. Finally, the final ranging result was estimated by the sum of the fine ranging value and coarse ranging value. Additionally, single reader and double-tag based geometric localization method was introduced to reduce the cost of hardware facilities. The simulation results show that, under multi-path environments, compared with the directly ranging with subcarrier phase, the average ranging error of double tags based two-step ranging approach is reduced by 35%, and the final average localization error is about 0.43 m, and the maximum error is about 1 m. The proposed approach can effectively improve the accuracy of phase based localization technology and also reduce the hardware cost.