Passive Coherent Location (PCL) technology involves detecting and tracking objects using signals emitted by non-cooperative sources such as commercial broadcast and communications signals (e.g., FM radio, television broadcasts, cellular signals). PCL systems consist of multiple geographically dispersed receivers that intercept these signals as they reflect off objects in the environment. By analyzing differences in the arrival times and phases of signals received across receivers, PCL systems can triangulate target positions through a process called multilateration. This technique allows PCL systems to provide surveillance and tracking capabilities without emitting active radar signals, making them suitable for applications where stealth and low observability are critical considerations, such as border surveillance, surveillance airspace and urban security.
Cooperative passive coherent localization (CPCL) is a variation of PCL technology that integrates signals from cooperative transmitters, such as FM radio stations, television broadcast towers, or cellular base stations. Unlike traditional PCL systems that rely solely on non-cooperative signals, CPCL systems use these known transmitters to improve the accuracy and reliability of target location and tracking. Cooperative transmitters provide known reference signals that help improve the accuracy of multilateral calculations performed by the CPCL system. This approach allows CPCL systems to achieve more accurate geolocation results compared to standard PCL systems, especially in environments with limited or sparse non-cooperative signal coverage. CPCL Technology offers cost-effective surveillance capabilities and can operate covertly without emitting detectable radar signals, making it suitable for military reconnaissance, intelligence gathering and civilian applications such as emergency response and disaster management .