Charge-Coupled Device (CCD) Adaptive Discrete Analog Signal Processing

A CCD adaptive signal processor is described which uses a so-called "clipped-data" least mean square (LMS) error algorithm to optimize the selection of tap weights in a CCD filter. A detailed description of a 16-tap monolithic silicon CCD analog adaptive filter is also presented. The filter is comprised of a basic linear combiner formed with a nondestructively tapped CCD analog delay line and electrically reprogrammable MOS analog conductances as the tap weights. Two methods of varying the analog conductance are discussed: 1) variable VGSwith fixed threshold voltage VTand 2) variable VTwith fixed VGS. The former is performed with a CCD bidirectional charge control weight adjustment, whereas the latter is accomplished with MNOS memory transistors. To demonstrate the feasibility of adaptive analog signal processing, a 2-tap weight CCD adaptive filter is described and experimental results presented. Applications include optimum filtering, prediction, noise cancellation, and system modeling.