Characteristics of coplanar waveguide on lithium niobate crystals as a microwave substrate

A finite ground coplanar waveguide (FG-CPW) on lithium niobate (LiNbO3) substrates, without a thin SiO2 buffer layer, was experimentally characterized by using on-wafer measurements. The dielectric constant and the characteristic impedance were extracted from calibrated measurements made at up to 20GHz using the FG-CPW method. The loss tangent was then obtained by the conformal mapping approach after the dielectric constant and characteristic impedance had been accurately extracted. The dielectric losses of LiNbO3 substrates are not negligible even in the X band.