This project is part of a larger work to be developed during the PhD program of both the proposers. The main objective of this research proposal is to define and develop innovative techniques for the target motion estimation in all its aspects. The applications to which this study is addressed are mainly based on the field of maritime surveillance, but can also be extended to other targets or areas of interest. In particular, this work wants to exploit both active and passive radar systems in order to have the full knowledge of the target motion.
First, the estimation of the target translational motion by using multistatic active ISAR acquisitions will be performed. Particularly, we want to define a decentralized scheme that exploits the single sensor estimation of specific signal parameters (i.e., Doppler frequency and Doppler rate) to estimate the kinematic parameters.
Then, the estimation of the target¿s velocity using a passive radar system based on multiple GNSS transmitters of opportunity will be carried out. Particularly, we will propose an approach based on bistatic range, Doppler and Doppler-rate measurements obtained by multiple bistatic transmitter-receiver pairs.
In both the radar scenario, the Doppler-rate information, extracted by means of conventional techniques (for example contrast maximization) at single sensor level in the first case and to previous detection stages based on Doppler rate-driven migration compensation procedures, is used as an innovative measure not conventionally used for motion estimation that will provide an enhancement in the estimation procedure.
Among the goals of this project, we want to develop these techniques, verify their effectiveness with simulated analysis, and, if possible, validate them with real data acquisition campaigns, by also extending their use to other applications besides those for maritime surveillance.
The whole project is characterized by highly innovative contents since it aims at improving conventional techniques for the estimation of target translational motions and the target velocity/acceleration components by using the Doppler-rate information, which is not usually exploited in such contests.
The use of such additional measures could improve the system performances in both active and passive scenarios, since it provides an improvement in estimation accuracy with respect to the conventional approaches based on the Doppler information only. It can be seen how the exploitation of the Doppler-rate information can improve the estimation of the target's velocity/acceleration parameters, especially for cases of low angular diversity of the sensors for the first case and of the transmitters of opportunity for the latter.
First preliminary results of such approaches have been presented by the proposers during the International Radar Symposium 2021, where the robustness of the exploitation of the Doppler-rate both in active and passive techniques has been proved for maritime surveillance applications. In this research proposal we want to further improve the work presented at the IRS conference in terms of efficiency and expand it for other implementations besides those of maritime surveillance by using other targets of opportunity such as vehicles and/or airplanes. We would like to carry out a feasibility study and, if possible, acquisition campaigns with real data to validate the approaches.
Regarding the ISAR case, the new improvements will be addressed by making an analysis of robustness with respect to non-ideal conditions and considering a broader sensor network. Finally, to measure the improvement, a comparison to centralized approaches will be performed.
Moreover, for the passive radar case, we want to improve the Doppler+Doppler-rate technique for the target velocity estimation and validate it for different types of target motion, not only for targets with constant velocity. We also want to explore the possibility of using an advanced linear array receiver, instead of a single receiver, which will also estimate the target direction-of-arrival (DOA) as an additional radar observable. Such information can be used to improve the accuracy of the target position estimation, thus leading to an improvement in the accuracy of the target velocity estimation, which depends on the target estimated position. It would also be interesting to study the possibility of exploiting for this purpose other satellite transmitters in addition to those of the GNSS, such as broadcasting satellites.
Finally, the proposed studies for the active and the passive scenarios will be applied together using both active and passive sensors in order to have full knowledge of the motion of the target and thus increase its information.