Adaptive interference rejection in a digital direct sequence spread spectrum receiver

To improve system performance in the presence of continuous-wave (CW) interference, a 2-b analog-to-digital converter (ADC) with adaptive thresholds has been implemented in a DSSS (direct-sequence spread-spectrum) receiver for code-shift-keyed signals. The theoretical and measured system performance of a hard limiter and the adaptive 2-bit ADC to accomplish analog-to-digital (A/D) conversion in the DSSS receiver are compared for AWGN (additive white Gaussian noise), CW, and combined AWGN-CW interference. The system´s dynamic response to changes in signal or interference conditions is investigated by means of Monte-Carlo simulations. Both steady-state and dynamic behavior of the 2-b ADC are satisfying in the presence of strong CW interference. However, if the AWGN contribution is dominant, there is no significant difference in the performance of the hard limiter and the 2-b ADC