An Adaptive Kalman Filter Excisor for Suppressing Narrowband Interference
DEFENCE RESEARCH ESTABLISHMENT OTTAWA (ONTARIO)
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Several reports have been written by the author which characterize the performance of a Kalman filtering technique to suppress narrowband interference from direct sequence spread spectrum communications systems in a non-adaptive context, i.e., when the user has some a priori knowledge of the interference characteristics. This report expands on this technique by presenting an adaptive scheme which is useful for the situation when the interference characteristics are unknown. In this context, the Kalman filter must learn to achieve optimal performance through the adjustment of one of its parameters. The criterion for optimality is the minimization of the mean-squared error at the output of the canceller, where this error consists of spread spectrum signal, noise and residual interference. The reasonable assumption is made that minimizing the mean of this squared error with respect to the appropriate Kalman filter parameter is equivalent to minimizing the mean squared value of the residual interference. Examples of the dynamic behaviour of the adaptive interference suppressor are presented for narrowband Gaussian noise interference with bandwidths ranging from 1 to 5 of the chip rate.
- Radio Countermeasures
- Electricity and Magnetism