On the application of time-frequency distributions in the excision of pulse jamming in spread spectrum communication systems

Direct sequence spread spectrum (DSSS) systems are widely used in in a variety of applications including the suppression of a strong interfering signal due to jamming or multipath propagation. Time-frequency distributions (TFD) are applied for interference excision in spread spectrum communication systems. The focus is on jammers consisting of pulses of constant envelope frequency modulated interference. The time-support and the instantaneous frequency (IF) information provided by the TFD are used to reduce the jammer effect on the receiver performance. This is achieved by applying an excision notch filter with a null placed at the interference IF. The filter is turned on and off in synchronisation with the interference duty cycle. The bit error rates at different frequencies are given and compared with those obtained using multiresolution analysis.