Abstract
This paper describes a study on a new type adaptive noise canceller for periodic interference. The usual adaptive noise cancelling system is controlled by a clock pulse whose frequency is determined a priori considering the frequency band width of the reference input. On the other hand, the adaptive filter proposed in this paper is designed to operate synchronously with the reference input, that is, the frequency of its clock pulse varies in proportion to the fundamental frequency of the reference input. For the purpose, the phase-locked loop is used. It captures the fundamental frequency component of the reference input and generates synchronizing pulse. Synchronous operation yields such profit that the total computational cost decreases to about 1/2N times as compared with the usual nonrecursive adaptive filter, where N is the number of weight coefficient of the adaptive filter. It is a great help not only in simplifying the hardware construction but also in widening operational frequency range of the adaptive filter.
This paper presents theoretical investigations on the notch characteristics of the synchronous adaptive filter. And it is experimentally shown that the proposed adaptive filter has excellent performance.
