Adaptive line enhancers with discriminated structures

The adaptive line enhancer eliminates noise from a sinusoidal signal with the unknown frequency buried in the noise and extracts the sinusoidal signal. The performance of the adaptive line enhancer is represented by the signal-to-noise improvement figure. The signal-to-noise improvement figure increases as the bandwidth of the adaptive line enhancer is made narrower. The conventional adaptive line enhancer, however, contains an incompatible problem in that the convergence of the adaptive coefficient is deteriorated when the signal-to-noise improvement figure is raised by narrowing the bandwidth. This paper proposes the adaptive line enhancer with the discriminated structure to solve this problem. The adaptive line enhancer with the discriminated structure is composed of two parts. One is the (frequency) estimator that estimates the frequency of the unknown sinusoidal signal, and the other is the (sinusoidal signal) discriminator that discriminates the unknown sinusoidal signal from the noise. The estimator is the conventional adaptive line enhancer, and the bandwidth is determined so that the convergence of the adaptive coefficient is the fastest. The discriminator is the narrowband bandpass filter where the center frequency is controlled by the adaptation coefficient. This paper presents the optimal design method for each of those parts, and the effectiveness of the method is verified by a computer simulation.