Optimum linear filtering for charge-transfer devices

Abstract

A method of filtering analog signals transferred through a charge-transfer device (CTD), which is capable of greatly reducing the distortion introduced by incomplete charge transfer, is suggested. By using transversal filters consisting in part of single CTD storage cells to achieve the necessary phase delay, the output charge packets can be combined in a manner which offsets the presence of incompletely transferred portions of charge acquired by the packet of interest. The transfer function of the filter is calculated directly from that of the CTD. Examples are given which indicate that in most cases of interest only a few filtering stages are necessary to reduce the distortion to 1 percent of its unfiltered size.