In order to produce high intensity exotic beams in the existing experimental rooms of the GANIL facility, the SPIRAL2 project is under development and under construction at GANIL. The first phase of the SPIRAL2 project consists to build a new accelerator composed of two sources, an ion source and a proton/neutron source, a RFQ and a superconducting Linac. The linac is designed to accelerate 5 mA deuterons up to 40 MeV and 1 mA heavy ions up to 14.5 MeV/u. A new electronic device has been developed at GANIL to measure phase and amplitude of pick-up signals and calculate the beam energy. The principle consists of directly digitizing the pick-up pulses by under-sampling. The Phase and amplitude of different harmonics are then calculated with a FPGA by an I/Q method before the beam energy calculation. This paper gives results of the peak-up tests in laboratory and the comparisons with simulations. The tests in laboratory and on the GANIL accelerator of an electronic prototype are shown and presented.