Adaptive interference rejection for non-coherent digital direct sequence spread spectrum receivers

Digital matched filters for direct sequence spread-spectrum communications are considered. Minimum complexity is obtained if hard-limiting analog-to-digital converters (ADCs) are used. However, while the digital matched filter receiver using 1-bit quantization performs well in additive white Gaussian noise (AWGN), system performance is flawed by threshold effects due to the limiter nonlinearity if deterministic interference statistics like those exhibited by continuous waves (CW) must be considered. The authors look at a 2-bit ADC technique. Analytical results for a noncoherent receiver, suitable for the processing of code shift keyed (CSK) signals, are presented, along with a brief review of ADC problems arising in digital direct sequence receivers operating in the presence of AWGN, CW, and combined CW/AWGN interference.