In this contribution, the feasibility of a short range ship collision avoidance system has been investigated. Based on microwave and millimeter wave radars, the system has the aim to accurately detect the presence and distance of possible obstacles inside the harbor. Indeed, whereas ships are usually equipped with long-range radars for the open see navigation, the in-harbor navigation relies only on the manual ability of the captain. An accurate model of the real scenario is proposed by taking into account obstacles of interest like small ships and shore structures. Different operating frequencies have been considered and evaluated, thus proposing a reliable system able to effectively assist the navigation. This contribution paves the way for enabling the concept of autonomous ship navigation by exploiting advanced sensing technologies.