This thesis is focused on the design of the Power Supply Board (PSB) of a Software Defined Radio (SDR) for micro-satellites system intended to be compatible with NASA Deep Space Network (DSN). The thesis work has been carried out with the Italian aerospace company Argotec in Turin. The aim of the thesis is in accordance to the objective of Argotec company of designing a SDR to be used for their own satellites and to compete with current SDR in the aerospace market. The focal point is the definition of the architecture of the PSB and so the definition of the converters that will be implemented during the fabrication and the design of the primary isolated converter.