In this paper an innovative solution leading to high performance/low-cost multi-domain T/R modules, utilizing emerging semi-conductor technologies such as GaN and SiGe, will be outlined. In particular a complete X-Band TRM MMIC chip-set based on GaN for the front-end RF functions and on SiGe multifunction chip for signal amplitude and phase control will be presented. The GaN front-end RF functions comprise state-of-the-art HPA, robust LNA and high power SPDT switch MMICs designed and fabricated by Selex Sistemi Integrati internal facilities. The SiGe multifunction Core Chip has been designed by Selex Sistemi Integrati employing a low-cost SiGe BiCMOS commercial process.