An adaptive line enhancer based on the convex combination of two IIR filters

An adaptive line enhancer is a self-tuning filter which attempts to retrieve a sinusoid buried in noise. Generally speaking, there is a trade-off between convergence speed and steady-state error. One method to address this is to use a variable step size algorithm, with a large step size for acquisition, and a smaller step size for improved steady-state performance. An alternate topology is based on the convex combination of two adaptive filters: a fast filter handles acquisition, while a slower filter is used to minimize error. In this paper, we present an adaptive line enhancer based on the convex combination of two IIR filters. It achieves both fast tracking and good steady-state performance, albeit at an increase in computational complexity.