[in Japanese]

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[in Japanese]

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[in Japanese]

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[in Japanese]

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[in Japanese]

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Improvement in the track-following servo for optical disk systems is described. The authors introduce an identity observer for state-feedback control and a stabilized repetitive control method based on modern control theory. The object of the identity observer is to increase stability and that of the control method is to trace accuracy. The out put of the identity observer is not disturbed by high frequency mechanical resonance, so the estimated velocity of lens movement can enhance gain crossover. The regulator system is apt to increase system deviation. To minimize this effect, the bandwith of the speed loop is limited. Repetitive control is also adopted to minimize steady-state errors. A neutral-type time-lag system such as repetitive control has an infinite number of poles in the s-plane, so it oscillates from time to time. Passband limitation and attenuation in the repetitive loop effectively compensate for this oscillation. As a result, the tracking servo system mentioned above has a gain crossover of 8.5 kHz and a phase margin of 70 degrees. No residual error can be observed up to 600, u m disk eccentricity.

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This paper discusses signal processing for a proposed EDTV system using an interlaced scanning TV camera. The encoding process, such as insertion of high resolution information, and the pre-combing process in the temporal-vertical frequency domain are described for both NTSC composite signals and component signals. Horizontal resolution of about 500 TV lines is obtained in still pictures and crosscolor in the moving area is greatly reduced with slight resolution degradation. The pre-combing method explained in this paper is useful for achieving higher quality in today's TV systems.

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This paper presents signal processing for progressive-interlace scan conversion using a progressive scanning TV camera. Spectrum analysis in the three dimensional frequency domain shows that use of a progressive scanning signal makes it possible to achieve aliasing free scan conversion and motion detection of the 30 Hz temporal frequency component. Interference caused by interlaced scanning is greatly reduced without any degradation of dynamic characteristics. A vertical helper signal which can improve vertical resolution in moving objects is also proposed.

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A digital facsimile broadcasting system multiplexed with a television sound channel has been studied in Japan. In this system, the digital facsimile signal is multiplexed by DQPSKFM modulation using a second subcarrier and is deteriorated by various disturbances in television reception. This paper describes deterioration of facsimile signals caused by ghost (multipath) disturbances and tuner distortion in facsimile receivers. The results show that deterioration is caused by the second harmonic of the sub sound channel and by cross modulation of the main and sub sound channels. Crosstalk from the digital facsimile signal to the sub sound channel when ghost influences occur is also discussed.

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[in Japanese]

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