Synergistic radar: a new approach to intrusion detection

The authors introduce a new electromagnetic sensor technology called synergistic radar as it is utilized in the RadioGuard intrusion detection product. This passive line sensor detects disturbances to commercial FM radio signals caused by an intruder moving in proximity to an open transmission line relative to the same radio signal received on a central reference antenna. The product utilizes a totally new type open transmission line and associated signal processing technique so as to determine the location of the intruder along the sensor line and to permit the use of exactly the same cable structure along the entire cable length. This new open transmission line was designed to be used buried beneath a surface, laying on a surface or suspended in air. By simultaneously processing signals from two or more FM stations the RadioGuard product provides redundancy in case of station failure as well as improved performance due to frequency diversity. The general principles of synergistic radar, the design of the open transmission line, and the specific signal processing techniques used in RadioGuard are described. The performance of this new sensor in various applications is compared to that of competing products