Patent ID: 7327794

Claim:
An apparatus for detecting a narrowband jamming signal in a block oriented digital transmission system, comprising: a filtering unit adapted to receive data from a channel selector for identifying a channel that is jammed; a masked channel selector adapted to receive an indication of a jammed channel from the filtering unit and to identify a predetermined number of channels adjacent to the jammed channel that are not identified as jammed; a jam mask memory adapted to store information that identifies the jammed channel and the predetermined number of adjacent channels not identified as jammed; wherein the filtering unit comprises, a filter adapted to receive data from the channel selector and adapted to provide an average power of selected channels different from a channel centered in the filter, and a comparator adapted to receive, from the channel selector, a power of the channel centered in the in the filter, adapted to receive a threshold value that is larger than the average power of the selected channels, and adapted to provide a signal to the masked channel selector for identifying the channel centered in the filter as a jammed channel if the power of the channel centered in the filter is greater than the threshold value.