The RF Phase Reference Distribution system followed by the LLRF control system must assure precise stabilization of the RF field withinthe accelerating cavities of the European XFEL accelerator. The required amplitude and phase accuracy respectively dA/A <3E-5, dphi<0.01 deg @ 1.3GHz in the injector and dA/A<1E-3, dphi <0.1 deg @1.3GHz in the main LINAC section. The RF synchronization systemwill distribute a harmonic phase reference signal from the Master Oscillator system to hundreds of devices distributed in the 3.4 kmlong facility. This contribution describes the proposed architecture of the distribution system which takes advantages of both coaxialand optical distribution links designed in order to provide a good compromise between performance, reliability and cost. Amongst themost important components are interferometers build to suppress phase drifts in coaxial cables. General concept, issues and achievementswill be presented together with results of prototype devices measurements performed to validate our concept
