A 12×12 Switch Matrix Unit featuring silicon RF MEMS assembled on LTCC boards has been developed under a Contract with the European Space Agency (ESA) for satellite communication application. The Switch Matrix is a complete Engineering Model unit, housed in a mechanical box in aluminum with RF coaxial connectors and DC connectors for powering and commanding. To the authors' knowledge, it is the first complex equipment realized in Europe exploiting the advanced features of the RF MEMS and multilayer LTCC technology to achieve a significant mass and size reduction. Full wave simulations of entire structure are reported, as well as test results. Their agreement is good up to the satellite downlink C-band (3.7–4.2 GHz). An insertion loss of −20dB, return loss of −10dB and isolation of 40–45dB have been measured. The matrix is passive (not provided with amplifiers), having a DC power …