Multilevel storage memory using serial—parallel–serial charge—coupled device

Abstract

Since the CCD can handle analog signals directly, it is used widely for delay lines, filters, imaging elements and imaging memories. This paper considers the multilevel storage memory of an SPS (serial‐parallel‐serial)‐CCD applied to field memories of image signals. First, a charge transfer model for an SPS‐CCD is created. By means of the transfer function derived from this model, it is clarified that the transfer losses of the serial register and the parallel register degrade the frequency characteristics of the amplitude and phase. It is pointed out that this degradation can be improved significantly by compensation of the transfer losses of the two serial registers and the parallel register. Since realization of a circuit for rigorous compensation of the transfer loss is extremely difficult, a simple transfer loss compensation method is also studied in which the SPS‐CCD is considered as a cascade connection of two serial registers. It is found that the difference in the effect of simple and rigorous compensations is at most 0.6 percent in the case of 50 percent eye degradation. Hence, the effectiveness of the simple compensation is confirmed. Also, by using a commercially available CCD, an experiment for eight‐level storage memory is carried out in which a simple transfer loss compensation is applied. It is confirmed that agreement of the calculated and measured signal error rates is excellent.