Modulation choices for LPI/LPD communication systems

Summary form only. The need for low probability of intercept/low probability of detection (LPI/LPD) systems has been recognized by the military and civilian agencies. Industry´s first attempts at developing such systems were based upon the use of traditional spread spectrum techniques such as frequency hopping and pseudonoise spreading with a lowered transmitted power. Subsequent research and testing has shown that lowering the power on traditional spread spectrum systems does not make them LPI. Research at the Naval Command Control and Ocean Surveillance Center, RDT&E Division Detachment Warminster, PA (NRaD Detachment Warminster) has centered on the development of waveforms that are not detectable using either energy detectors or feature detectors. NRaD has sponsored corporate research and development, as well as performed in house research and development of communication waveforms that are intended to defeat various types of feature detectors. This paper addresses potential threats to communication signals and then discusses the results of various programs to develop waveforms that defeat some of these threats. The detection of LPI/LPD signals will most likely be performed with special advanced detectors, and not simple radio systems. These advanced detectors mostly fall into a category known as feature detectors. As the name implies, feature detectors target certain highly detectable features of the LPI waveform such as the carrier, chip rate, hop rate, etc. Concerns for airborne LPI are also discussed