An L-Band high power and efficient solid state power amplifier (SSPA) designed for the European satellite navigation system (i.e., Galileo) is presented. The developed SSPA, based on European Gallium Nitride (GaN) technology, comprises all the circuits required to interface the module with the satellite bus (i.e., a Power Supply Unit, PSU), and to control its functionalities by remote telecomand and telemetry (i.e., an Electronic Power Conditioner unit, EPC). The Radio frequency Unit (RFU) together with the PSU and EPC are accommodated in a single box with limited volume and mass. In continuous wave operating mode, the SSPA delivers an output power higher than 300W at less than 3 dB of gain compression in the whole E1-Band (i.e., center fre...