Olmi R, Bini M, Ignesti A, Riminesi C
IROE-CNR, Firenze, Italy.
J Microw Power Electromagn Energy. 2000;35(3):135-43. doi: 10.1080/08327823.2000.11688430.
Many applications of microwave energy to wooden materials have been developed in the last few decades, both for treatment and for diagnostic purposes. All these applications require a reliable estimation of the permittivity of the wood species of interest, which is the physical parameter of crucial importance in the absorption of electromagnetic energy. This paper presents results obtained in the dielectric characterization of five wood species in the frequency range from 2 to 3 GHz, including the ISM frequency of 2.45 GHz. Permittivity was measured by an open-ended coaxial-line probe of new design on wood samples conditioned at several moisture levels. The influence of the natural variability of wood characteristics on the measured permittivity was also investigated by a suitable experimental setup consisting of a poplar table including both sapwood and heartwood regions. Finally, a theoretical discussion on the meaning of a scalar measurement on anisotropic dielectrics is conducted in terms of an isotropic-equivalent permittivity, which is related to the permittivity tensor of the dielectric material.
在过去几十年中，微波能量在木质材料上有许多应用，包括处理和诊断用途。所有这些应用都需要可靠地估计感兴趣木材种类的介电常数，这是电磁能量吸收中至关重要的物理参数。本文介绍了在2至3 GHz频率范围内对五种木材进行介电特性表征的结果，包括2.45 GHz的工业、科学和医疗（ISM）频段。使用新设计的开口同轴探针在不同含水率条件下的木材样品上测量介电常数。还通过一个合适的实验装置研究了木材特性的自然变异性对测量介电常数的影响，该装置由一张包含边材和心材区域的杨树桌子组成。最后，根据与介电材料介电常数张量相关的各向同性等效介电常数，对各向异性电介质标量测量的意义进行了理论探讨。
