THIS PAPER will describe the organization, performance and application of a newly developed multi-purpose CCD, which has two combing functions and a simple delaying function. Figures 1 and 2 show a schematic diagram and a photomicro-graph of the device, respectively. The filter consists of a main CCD delay channel and two sub CCD delay channels, which are terminated at two comb outputs ( Y and C) and a simple delayed output (D). If the device is operated at 14.4MHz sampling, which corresponds to four times the color subcarrier frequencywhere fH is horizontal scan rate 15.75kHq the first order combed luminance, chrominance and simple delayed (almost 1H) signal are obtained from the Y, C and D outputs, respectively, when the composite video signal is applied to the inputs. By dividing the input portion of the main channel by four parts, each of which had exactly the same structure as the sub-channel input, the amount of carriers flowing into each charge mixing point were made equal to obtain a high rejection ratio". The surface channel potential equilibration method was employed at each input to realize low distortion. The delay stage active area (buried N-channel) was reduced to 1.3 x 3.0mm by employing race track corners. The same wideband (>5OMHz) output circuit, consisting of a gated charge detector followed by a three stage source follower, was used at each output.was carried out at the same time for all the inputs, sampling time error, which causes notch frequency shift**, was kept at almost zero. Therefore, high rejection ratio and small notch frequency shift were easily obtained as the transfer inefficiency was small.This was not the situation in 3 X fsc sampling devices'. Experimental ResultsFor the 4 X fSC sampling CCD comb filter, as charge samplingRejection ratios for the luminance and chrominance signals were greater than 35dB within the full Nyquist bandwidth; Figure 3. Maximum notch frequency shifts for both signals were less than 30Hz. Transfer inefficiency estimated from the shifts was less than 7 x per transfer. Differential gain (DG) and differential phase (DP) of the chrominance signal were less than l%and 1.5', respectively, regardless of the average picture level ~ *Rejection ratio is the amplitude response at a tooth fredivided by that at the adjacent higher notch frequency (NfH for quency ((2N+l)fH/2 for chrominance, NfH for luminance) chrominance, (2N+l)fH/2 for luminance).minimum response frequency and notch frequency.(APL), for the NTSC lVpp (10 step staircase) linearity test signal.These values were brought about by the effect of dc clamp circuits shown in Figure 1, as well as by distortion cancellation obtained by applying the input signal to both IG2 and IG1. Meanwhile, the distortion in the simple delayed signal was slightly larger(DG=2.5% and DP=1.5') than that in the chrominance signal because of no cancellation effect. Signal-to-noise ratio within the full Nyquist bandwidth for lVpp input reached 60dB(pp/rms) for both signals.order comb filter to separate luminance and chrominance ...
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