Telecommunication and automotive industry requires high volume and low cost circuit fabrication, while at the same time demanding excellent electrical performance, reliability, circuit miniaturization and surface mounting techniques. Today, the multilayer LTCC (Low Temperature Co-fired Ceramics) technology is getting more attention for millimetre wave applications, and is often chosen because of its high degree of integration and its high-reliability properties.This technology is being installed in our laboratory at Telecom Bretagne and the commercial ESL41110 tape was selected to make our first RF LTCC circuits. This tape was characterized at ESL (Electro Science Laboratory) from 3 to 19 GHz, and the substrate properties such as dielectric constant and insertion loss are given in [1].