Wireless Distributed Frequency and Phase Synchronization for Mobile Platforms in Cooperative Digital Radar Networks

To continue improving the performance of modern communications and radar remote sensing systems, the implementation of distributed radio frequency (RF) systems has become an increasingly active area of research. One major obstacle to implementing such a distributed network is achieving highly accurate synchronization of all RF electrical states – time, carrier phase, and carrier frequency – as without such synchronization, coherent operation amongst all systems in the network is impossible. Many techniques for achieving synchronization are not accurate enough for application in RF phase and frequency synchronization and thus cannot be applied in such networks. Others are hardware-based, making them difficult to apply to legacy systems. Moreover, many synchronization procedures require external references for establishing synchronization of one or more of the RF electrical states, limiting their application to scenarios where such external references are unavailable. Finally, many techniques are not tolerant of relative motion between platforms, making them less useful for systems such as distributed synthetic aperture radar (SAR) systems. In this paper, an RF synchronization procedure is proposed. Though its intended application is distributed radar sensor networks, it is applicable to any distributed network requiring RF coordination, such as distributed RF communication systems. The technique is capable of achieving synchronization of time, carrier phase, and carrier frequency, and can do so without external references or additional hardware. Moreover, the technique is scalable to large networks and is capable of compensating for relative motion-induced synchronization errors. The proposed technique is validated in simulations for a wide variety of operating conditions, and a three-sensor distributed SAR simulation is provided to demonstrate the effectiveness of the proposed technique in a mobile distributed radar scenario.