MINIMIZING THE EFFECT OF JAMMING THROUGH THE USE OF WIDEBAND HF

HF IS USED EXTENSIVELY TO SUPPORT BEYOND-LINE-OF-SIGHT (BLOS) COMMUNICATION REQUIREMENTS. IN GENERAL THESE LINKS ARE BOTH EASY TO EXPLOIT AND EASY TO JAM. FREQUENCY HOPPING TECHNIQUES HAVE BEEN USED WITH LIMITED SUCCESS AGAINST THIS JAMMING. FURTHER, THE DATA TO BE TRANSMITTED IS CONSTRAINED TO HAVE LOW BIT RATES. THIS PROPOSAL DESCRIBES A NOVEL APPROACH TO IMPROVE JAM RESISTANCE AND TO ASSURE LPI AND LPE. THE TECHNIQUES USED INCLUDE SHARPLY FILTERED TRELLIS CODED FM TO PROVIDE LPI AND LPE; DIRECT SEQUENCY SPREAD SPECTRUM OF THE HF SIGNAL TO ACHIEVE A WIDE BANDWIDTH AND REDUCE FADING; AND NARROWBAND EXCISION USING THE FFT TO MINIMIZE THE EFFECT OF JAMMERS.