Lagrange-Polynomial-Interpolation-Based Keystone Transform for a Passive Radar

In this paper, we address the problem of target's range migration in passive bistatic radar exploiting long coherent integration times with fairly wideband signals of opportunity. We resort to the well-known keystone transform (KT) to compensate for the range walk effect and to take advantage of a higher coherent integration gain against targets with nonnegligible radial velocity. Specifically, an efficient implementation of the KT is proposed, based on the Lagrange polynomial interpolation, in order to reduce the computational load of the method that mostly depends on the required slow-time interpolation stage. The analysis conducted against simulated data shows that the conceived approach allows us to achieve theoretical performance, while further reducing the KT complexity with respect to alternative solutions based on cardinal sine functions or chirp-Z transforms. Moreover, the application against experimental datasets collected by a DVB-T-based passive radar proves the practical effectiveness of the proposed algorithm and highlights its suitability for real-time air traffic surveillance applications.