This paper presents the pioneering results of successful target detection using a fully operational and cooperative 5G cellular network as a source of illumination in a passive radar system. The electromagnetic wave generated by the real-life base station allowed for remote sensing of a moving car in bistatic geometry, which shows the feasibility of passive radar in which new generation radio networks serve as an illuminator of opportunity. The paper describes passive radar principles, the theoretical fundamentals of the 5G signal structure, and proposed processing for 5G network-based passive radar. Also, the 5G passive radar demonstrator is described, and the trial results showing the possibilities and limitations of using new radio standards in the context of passive radars.

This paper presents an alternative processing chain for the passive radar using fifth-generation (5 G) standard technology for broadband cellular networks as illuminators of opportunity. The proposition is to use a 5 G synchronization signal block's (SSB) periodically transmitted modulated pulse in 5G-based passive coherent location (PCL) system processing. Although the SSB periodicity limits the velocity ambiguity, the paper describes a solution to tackle this problem in a single target scenario. The method is advantageous when there is a lack of transmission in the telecommunication channel, and the 5 G SSB is the only existing signal. The paper proposes a signal processing pipeline for 5G-based PCL that is inspired by passive radars using non-cooperative pulse radar as an illumination source. The method has been validated using simulated and real-life 5 G data measurements. The results presented in the paper show the possibility of detecting a moving target with a lack of data transmission in the 5 G network, using only the SSB when the classical passive radar signal processing fails. The presented results prove the possibility for a significant increase of 5 G network-based PCL utilization in short-range applications.

In recent years, the 5G network has been deployed more and more densely. The signal coverage area is increasing, and in many countries, it allows the use of the new radio (NR) in most large cities. This makes it possible to use 5G network signals for telecommunication and remote sensing purposes. This article describes the opportunities and limitations of using 5G signals for radars. The waveform characteristics of the 5G network were tested and compared, range analyses were made, and the possibilities of detecting targets using impulse signals sent for various purposes in the network were examined. The article presents measurable properties of 5G signals that allow one to detect targets. Also, possibilities of exploiting 5G signalling for radar applications are provided. Moreover, the main limitations of using 5G waveforms and the general 5G architecture for radar purposes are discussed. Finally, a preliminary concept validation is shown with experimental results of car detection using 5G network-based passive radar.

This paper presents the first successful drone detection results using a 5G network as a source of illumination in a passive radar system. Furthermore, a novel adaptive strategy for signal integration is shown. The proposed approach is based on the Rényi entropy. It allows one to select time frames with a densely allocated downlink channel both in the time and frequency domains. The resource allocation is strongly related to a network load and has a crucial influence on 5G-based passive radar range resolution and detection capabilities. The proposed technique was validated using simulated and real-life signals, confirming the possibility of detecting unmanned aerial vehicles (UAVs) in 5G-network-based passive radars. Moreover, the proposed methodology can be directly used in passive radar systems where the illuminating signal duration and bandwidth are content-dependent, and the radar resolution may vary significantly.

This article deals with the problem of detection performance prediction for passive bistatic radars that use illuminators of opportunity, such as radio or television transmitters. First, a simplistic free-space propagation model is introduced. Next, the effects of the transmitter and receiver antenna patterns are analyzed. Then, the influence of the pattern-propagation factor is investigated, considering the elevation patterns, multipath, and diffraction. The performance prediction of the free-space model and a more realistic model with antenna patterns and propagation effects are compared. The variation of the echo power level caused by the propagation effects predicted in the simulations is verified with real data acquired with an FM-based passive radar. The presented approach allows for a more realistic prediction of the passive radar performance to be achieved in comparison with a simple free-space propagation assumption. Some examples of passive radar performance optimization using the introduced methodology are presented.

This article presents the data fusion results of integrating several multiband active and passive radar sensors for enhanced situational awareness. The two sensor technologies come with partially complementary properties, thus a suitable mix provides improved performance in a couple of situations of operational interest. The presented results have been obtained during a trial measurement campaign of the NATO Science and Technology Organization, which took place on 3–13 September 2019, in Poland. Held under the code name Active Passive Radar Trials—Ground-based, Airborne, Sea-borne (APART-GAS), this trial campaign was attended by over 70 participants from 10 countries. It covered many new predefined military scenarios tested in real time. This article's results verify and validate the Deployable Multiband Passive Active Radars (DMPAR) concept developed during previous work by various NATO research groups.