Limitations of multilevel storage in charge-coupled devices

The feasibility of applying multilevel storage (MLS) in charge-coupled devices (CCD's) is demonstrated. The effect on the allowable number of levels of the different noise sources in the CCD, the input-signal power, the charge-handling capacity, and the effective bandwidth have been considered. Accurate noise measurements, by means of statistical correlation are presented. With eight levels of charge, three bits of data have been achieved in one storage cell with two-phase stepped-oxide double-polysilicon CCD's, and detected with an average error probability of 2 x 10 to the -10th. Four bits of data in one storage cell could be achieved in similar devices with a charge-transfer inefficiency of epsilon not greater than 0.001 with an average error probability of less than 9 x 10 to the -8th.