利用矩形波导管和向量分析仪,测量了几种液晶材料在26.5～40 GHz波段(Ka波)的介电常数.实验表明,1 kHz频率下呈现正、负介电各向异性的液晶材料,在该微波波段下都显示为正的介电各向异性.尽管这些材料的静介电常数各向异性相差很大,但是该微波波段对应的介电各向异性相差却很小,而且在26.5～38 GHz区间内几乎不随频率的增大而发生变化.
A reflection-type liquid crystal (LC) test cell prepared with a K-band rectangular waveguide is used to determine the dielectric constant of LC materials. It is found that the usual LCs showing positive or negative dielectric anisotropy in 1 kHz reveal positive dielectric anisotropy in millimeter wave region. Furthermore, the high frequent dielectric anisotropy shows slight difference among the LCs and weakly frequency dependency between 26.5～37 GHz.
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