A Low-Impedance Coplanar Waveguide Using an Sr[TiO.sub.3] Thin Film for GaAs Power MMIC's

A novel structure for coplanar-waveguide transmission lines with low impedance and low loss is demonstrated in this paper. The new structure simply has a high dielectric Sr[TiO.sub.3] thin film underneath the coplanar conductors. Due to the high dielectric constant of Sr[TiO.sub.3], the coplanar line exhibited characteristic impedance as low as 18 with a slot width of 5 [micro]m and the center conductor width of 50 [micro]m, while a conventional coplanar line on GaAs showed only 30 [Omega] with the same configuration. The newly developed coplanar structure is easily applicable for present GaAs monolithic-microwave integrated-circuit (MMIC) technology, especially for power MMIC's and low-impedance devices. Index Terms--Coplanar waveguides, impedance transfomers, MMIC's, SrTiO.