Multiband passive radar for drones detection and localization

For many surveillance systems, a multisensory architecture is essential when aiming at providing accurate and reliable surveillance of critical infrastructures and protected areas. This is certainly the case for airports, harbours, prisons and chemical facilities as well as for public places such as parking areas, train stations or stadiums, especially due to the new and emerging threat represented by commercial drones and unmanned aerial vehicles (UAVs). In particular, their small size, low radar reflectivity and flexibility of manoeuvre make them especially difficult to detect, localize and classify. The potentials of passive radar (PR) in counter drone operations, by exploiting different illuminators of opportunity (IOs), such as DVB-T, DAB, GSM, WiFi, GNSS (Global Navigation Satellite Systems) and DVB-S that were introduced in previous chapters, have been recently investigated in several works. The reported results demonstrate that such sensors could be effectively employed for detecting and localizing small and medium drones up to a few kilometres from the PR receiver when DVB-T transmissions are exploited. However, in urban areas and highly populated environments, where the use of the non-invasive and green PR technology represents an attractive solution for enhancing the security level, it is important to consider the possibility to exploit a multisensory system by integrating PR with multiple operational frequency bands. The integration of PRs operating at different frequency bands can be obtained using two approaches: 1. A hardware integration can be conceived that provides a single multiband sensor, which exploits a common multichannel receiver, common data memory and common processing techniques for different signals of opportunity and therefore greater frequency bandwidth. 2. At functional level, where each sensor operates with independent receiving structures but the outputs of the multiple sensors are combined to provide improved performance. In the following sections, we proceed as follows. First, in Section 7.2, we briefly review the most attractive sources of opportunity for an anti-drone PR with their characteristics and signal processing requirements. Three specific sources of opportunity are identified that appear to be well suited for a multiband operation due to the complementarity of their characteristics. Therefore, we illustrate the concept of the multisensory system on the basis of the parasitic exploitation of such signals and discuss possible implementations and benefits. The different components of the multisensory system are then separately addressed in Sections 7.3–7.5 which are devoted respectively to anti-drone PR based on DVB-S satellite broadcast signals, DVB-T terrestrial TV and WiFi, in order to analyse the specific characteristics of their sensors as well as their performance. This analysis also allows to identify hardware and signal processing requirements for an effective implementation of the integrated multiband PR system.