The metrication of low probability of intercept waveforms

Abstract

In recent years, military radar operators have been concerned that the transmitted radar signals will beacon the presence of the radar to an enemy. If intercepted, the radar signals alert a target to an attack which could prompt evasive measures or countermeasures to be taken by the target including the possibility of a reprisal attack using an antiradiation missile. Furthermore, intercepted signals can divulge operating parameters of the radar to the enemy. In response to this low probability of intercept (LPI) requirement, waveforms have been designed to minimize the probability of intercept by an enemy receiver. These are largely based on the use of low peak powers and spread spectrum waveforms offering large processing gains. The interception of signals is a function of both the transmitted radar waveform and the intercept receiver. The aim of this work is to deduce a metric which may be used to quantify and hence compare how “discrete” many of the commonly used LPI radar waveforms actually are. This study considers the following LPI waveforms [1]: Linear Frequency Modulation (LFM), Sinusoidal Frequency Modulation (Sin FM), PolyPhase Shift Keying (PPSK) techniques including Frank, P1, P2, P3, and P4 codes Costas code Frequency Shift Keying (FSK), and Costas-Barker Hybrid (FSK/PSK). This work represents the first attempt to be published in the open literature to quantify the LPI properties of transmitted radar waveforms. Secure waveform coding strategies to minimize the risk of divulging radar capabilities is known as low probability of exploitation (LPE) and is not considered here.