Coherent Radar Networks: Terminology, Synchronization, and Applications

In coherent radar networks, multiple radar sensors not only operate cooperatively but also facilitate coherent evaluation of signals from other spacially distant radar units. This overcomes the limitations of single radars, enabling extended apertures and new multistatic sensing geometries. Applications are manifold, ranging from network-based direction of arrival (DoA) estimation to bi-/multistatic synthetic aperture radar (SAR) and joint communication and sensing (JCAS). In recent years, this has led to significant research interest and the design of a wide range of radar networks and synchronization concepts. This paper introduces a unified terminology and a general signal model applicable to radar networks and bistatic radars. Building on this model, this work provides a detailed review of the main sources of synchronization errors and their impact on radar signal processing. The paper further surveys and categorizes synchronization strategies proposed in the literature to address these errors. It thereby enables both a structured comparison of current radar networks and the design of novel network and synchronization concepts for emerging applications. To illustrate the potential of these approaches, three applications are presented in detail: a novel DoA estimation strategy for distributed radar networks, UAV-borne bistatic SAR, and JCAS.