Pseudo-Random Code Sidelobe Canceller

Abstract

During acquisition of direct sequence pseudo-noise signals, time sidelobes are produced at the correlator output which will degrade detection performance. These sidelobes may be the result of additive noise, channel distortions, deliberate jamming or the non-ideal correlation function of truncated code sequences. In order to minimize these sidelobes, special codes can be selected based on their low sidelobe levels, or some special sidelobe reduction or cancellation algorithm may be devised. A sidelobe cancellation algorithm for use with LSI correlators has been simulated. Segments of a maximum length code word as well as a totally random bit stream were tested. The simulation results show that the largest sidelobes are reduced by a small amount; however, the majority of the sidelobes are reduced by as much as 6 dB. Consequently the false alarm rate for a particular threshold setting may be reduced. A compatible technique for the derivation of a CFAR reference from the same correlator was also successfully simulated.