Personnel identification system utilizing low probability of intercept (LPI) techniques for covert operations

The paper documents the design of a laser/radiofrequency (RF) personnel identification (ID) system developed by Dynetics Inc., Harris Corp., and the US Army Communications and Electronics Command (CECOM). The ID system includes an interrogation unit with a programmable activation code. The interrogation unit consists of a directive, eye-safe laser and a spread-spectrum RF transceiver. This allows for a low probability of intercept (LPI) interrogation, which is of interest during covert operations. A responder unit is worn, for example, by a soldier and transmits an LPI spread-spectrum RF response, only after receiving the proper interrogation codes. The basic subsystems for the identification RF responder unit, and an electronic programming/synchronization unit. The operating principles for the subsystem are reviewed, and the design issues are discussed. In addition to the preliminary design performed under Phase I of the program, a breadboard system was developed to validate the proof-of-principle concept. Hardware implementation is reviewed and test results are presented. The prototype development and engineering plans are also presented