Pulse Jamming Effectiveness against a Spread-Spectrum Digital Voice Link

The effectiveness of a pulse jammer against a digital voice link using direct-sequence spread spectrum is considered. Voice digitization is CVSD at 16 kbps, so that a 10% bit error rate is selected as the criterion for acceptable speech intelligibility. The data modulation is DPSK. A fast AGC, wherein the attack and release times are very small in relation to the bit duration (62.5 microseconds), is shown to play an important role. A variety of pulse formats are considered, including multiple-bit and partial-bit pulse widths. In all cases it is found that pulse jamming is not an effective strategy against digital voice, but can be effective against data where a lower BER is required. Also, it is shown that the optimum jammer always entirely overlaps one data symbol in a DPSK format.