Selection of coefficient for equalizer in optical disc drive by golden section search

A digital signal is distorted in its amplitude and phase while passing through transmission lines and amplifying stages. An equalizer compensates this distortion for a signal to have uniform characteristics over all frequency range. Especially, the equalizer minimizes a noise and an inter-symbol inference (ISI) of a signal by compensating the attenuation in high frequency range. In case of an optical disc drive (ODD), the noise and ISI are aroused by the fluctuation of optical paths, the variation of tracking and focusing servo, the crosstalk of inter-tracks, etc. And they degenerate the jitter, a criterion of the quality of a signal, which makes it hard to judge a binary signal. The equalizer equipped in ODD improves the jitter by adjusting its coefficient. Generally, the coefficient of the equalizer is determined by the sequential search. The sequential search can be easily implemented because of its simplicity. But, it is hard to cope with the system fluctuation and the search speed is slow. This paper proposes a search method for the coefficient of an equalizer by using the golden section search (GSS), which deals with the system fluctuation better and improves the search speed.