空气与填充同轴探头测量生物组织高频介电特性差异性研究

Study on the difference of high frequency dielectric properties of biological tissues measured by air and packed coaxial probe

本文基于等效电路模型,对空气探头与填充探头测量生物组织高频介电特性的差异开展研究,为生物组织介电特性高频测量方法学提供参考。在100 MHz~2 GHz频段采用两种类型探头对不同浓度NaCl溶液进行测量。结果显示:由于测量时液体容易侵入探头内腔,空气探头测量计算结果的准确性与可靠性要低于填充探头,特别是被测物的介电系数,且NaCl溶液浓度越高误差越高。通过对探头终端进行覆膜可以阻止液体侵入,在一定程度上可提高测量准确度。但随着频率的降低,膜对测量的影响增大,测量准确性也随之降低。研究结果表明:空气探头尽管尺寸设计简单且容易定标,但在实际测量中与传统等效电路模型存在差异,实际使用时需要重新对模型进行修正。填充探头与等效电路模型匹配度较高,因此具有较好的测量准确性和可靠性。

In this paper,the differences between air probe and filled probe for measuring high-frequency dielectric properties of biological tissues are investigated based on the equivalent circuit model to provide a reference for the methodology of high-frequency measurement of biological tissue dielectric properties.Two types of probes were used to measure different concentrations of NaCl solution in the frequency band of 100 MHz-2 GHz.The results showed that the accuracy and reliability of the calculated results of the air probe were lower than that of the filled probe,especially the dielectric coefficient of the measured material,and the higher the concentration of NaCl solution,the higher the error.By laminating the probe terminal,liquid intrusion could be prevented,to a certain extent,to improve the accuracy of measurement.However,as the frequency decreased,the influence of the film on the measurement increased and the measurement accuracy decreased.The results of the study show that the air probe,despite its simple dimensional design and easy calibration,differs from the conventional equivalent circuit model in actual measurements,and the model needs to be re-corrected for actual use.The flled probe matches the equivalent circuit model better,and therefore has better measurement accuracy and reliability.