Wideband, Noncoherent, Frequency-Hopped Waveforms and Their Hybrids in Low-Probability-of-Intercept Communications
NAVAL RESEARCH LAB WASHINGTON DC
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Frequency hopping is a commonly used technique for achieving wide spread spectrum bandwidths in intercept-resistant and interference-resistant communications. This report develops the techniques necessary to determine the contribution of a frequency-hopped modulation to communication system detectability, independent of such scenario-related parameters as relative geometry, antenna gains, and link margins. A variety of frequency-hopped modulation schemes, associated processing techniques, and losses are discussed. Optimum intercept receivers are considered in order to place a theoretical bound on a signal detectability. This, in turn, leads to the development of quality factors which permit any analysis of the impact of waveform parameters alone on convertness. A parametric analysis is performed in terms of these quality factors for a large family of modulations. The result is a small subset of signals optimized for convertness, consisting of fast hop pulsed waveforms and slow hop continuous waveforms, both with pseudonoise hop bandwidth spreading. Selection of the final modulation must ultimately depeend on such additional system synchronization time, implementation complexity, and jam resistance. The impact of these factors is discussed qualitatively.
- Radiofrequency Wave Propagation
- Non-Radio Communications