Narrowband interference suppression using filter-bank analysis/synthesis techniques

The authors consider the application of multirate digital filter banks to the suppression of narrowband interference in direct sequence spread spectrum. In addition to providing a general framework from which to study and design transform domain interference suppression systems, these banks are a particular time-frequency distribution, making them applicable to a larger class of jamming scenarios. The authors exploit the bank´s perfect reconstruction property to mitigate on/off-type jammers. Quite practical filter banks are shown to provide near-perfect reconstruction while, due to superior filtering, effectively mitigating the spectral leakage problem with nearly complete removal of the interference. Bit error performance results are presented which demonstrate the superiority of the filter banks for a number of jamming scenarios. The mathematical-equivalent, computationally efficient processing structure known as polyphase filter networks is put forth and shown to possess only a slight complexity increase from windowed transform processing