A TRL-Like Calibration for Tunable Interdigitated BST Varactors

摘要

We report on a de-embedding technique for measuring the reflection coefficients of comblike capacitors patterned on barium–strontium–titanate (BST) ferroelectric films. The technique is derived from the thru–reflect–line calibration technique and is combined with conformal mapping to retrieve the complex permittivity of BST thin films. The accuracy of the method is demonstrated over a broad frequency for 0.3- $muhbox{m}$ -thick $ hbox{Ba}_{x}hbox{Sr}_{1 - x}hbox{TiO}_{3}$, with $x = 0.5$ , in a paraelectric state, grown by a sol-gel technique. The samples are characterized up to 35 GHz and exhibit a constant permittivity of 245 $pm$ 12%, which is in good agreement with the values deduced from propagation wave constants of BST transmission lines.