Extraction of FR4 Dielectric Properties in Microwave Bands Using ABCD Matrix

The extraction of FR4 dielectric properties in microwave bands by applying ABCD matrix is proposed. The method makes use of scattering parameters and calculating all kinds of device losses to get more accurate and reliable dielectric properties. By investigating the performance of a ungrounded coplanar waveguide straight line structure based on FR4 substrate, the dielectric properties of FR4 material are successfully extracted at 1-10 GHz range. The obtained dielectric properties are very close to the reference values, and it verifies the feasibility of the proposed method. The deviations of the extracted dielectric constant and dielectric loss tangent at 2 GHz/6 GHz/10 GHz are 0.026 (0.59%)/0.014 (0.32%)/0.022 (0.50^%) and 0.0053 (26.5%)/0.0009 (4.5%)/0.0002 (1%), respectively.