Oversampled sigma-delta adaptive filters for CDMA interference suppression

We present adaptive signal processing prediction architectures for narrowband interference (NBI) suppression for spread spectrum communication systems. The presented adaptive algorithm uses only 1-bit signals obtained from a front-end bandpass /spl Sigma//spl Delta/ converter. The adaptive prediction LMS filter uses a novel 1-bit technique and thus avoids all multibit PCM architectures. Using an f/sub s//4 system the QPSK demodulation as found in CDMA is also performed with 1-bit. Hence the complete architecture is almost all 1-bit and likely to be straightforward to implement as a custom ASIC. The paper presents results based on the oversampling ratio of the bandpass /spl Sigma//spl Delta/ converter and the effect on bit error rate of using this single bit NBI suppression architecture for spread spectrum CDMA.