The dielectric properties of biological tissues have been studied widely over the past half-century. These properties are used in a vast array of applications, from determining the safety of wireless telecommunication devices to the design and optimisation of medical devices. The frequency-dependent dielectric properties are represented in closed-form parametric models, such as the Cole-Cole model, for use in numerical simulations which examine the interaction of electromagnetic (EM) fields with the human body. In general, the accuracy of EM simulations depends upon the accuracy of the tissue dielectric models. Typically, dielectric properties are measured using a linear frequency scale; however, use of the logarithmic scale has been suggested historically to be more biologically descriptive. Thus, the aim of this paper is to quantitatively compare the Cole-Cole fitting of broadband tissue dielectric measurements collected with both linear and logarithmic frequency scales. In this way, we can determine if appropriate choice of scale can minimise the fit error and thus reduce the overall error in simulations. Using a well-established fundamental statistical framework, the results of the fitting for both scales are quantified. It is found that commonly used performance metrics, such as the average fractional error, are unable to examine the effect of frequency scale on the fitting results due to the averaging effect that obscures large localised errors. This work demonstrates that the broadband fit for these tissues is quantitatively improved when the given data is measured with a logarithmic frequency scale rather than a linear scale, underscoring the importance of frequency scale selection in accurate wideband dielectric modelling of human tissues.

中文翻译：

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对数和线性频率标度对组织介电数据参数建模的影响

在过去的半个世纪里，生物组织的介电特性得到了广泛的研究。这些特性用于大量应用，从确定无线电信设备的安全性到医疗设备的设计和优化。与频率相关的介电特性以封闭形式的参数模型表示，例如 Cole-Cole 模型，用于检查电磁 (EM) 场与人体相互作用的数值模拟。通常，EM 模拟的准确性取决于组织介电模型的准确性。通常，介电特性是使用线性频率标度测量的；然而，历史上曾建议使用对数标度更具生物学描述性。因此，本文的目的是定量比较使用线性和对数频率标度收集的宽带组织介电测量的 Cole-Cole 拟合。通过这种方式，我们可以确定适当的尺度选择是否可以最大限度地减少拟合误差，从而减少模拟中的整体误差。使用完善的基本统计框架，对两个量表的拟合结果进行量化。发现常用的性能指标，例如平均分数误差，由于平均效应掩盖了大的局部误差，因此无法检查频率尺度对拟合结果的影响。这项工作表明，当使用对数频率标度而不是线性标度测量给定数据时，这些组织的宽带拟合得到了定量改善，