A quantization-based watermarking system for motion pictures is proposed. In particular, methods for improving the image quality of watermarked video, the watermarking data tolerance, and the accuracy of watermark data detection are described. A quantitative evaluation of the reliability of watermarked data, which has not generally been discussed up to now, is also performed.

Sea ice clutter was measured using an X-band radar which is located at the city of Mombetsu in Hokkaido. The pulsewidth of the radar was 80 nsec. To sample by 40 nsec and record digitally, an emitter coupled logic (ECL) was used as a high-speed IC. The sampled data were first transferred to 64 Kbyte dynamic memory board and next to a 5 inch floppy disk through an 8 bit micro-computer. These data were processed by a 16 bit micro-computer. As a result, it is shown that the amplitude of sea ice obeys a Weibull disturibution with shape parameters of c0.50 to 1.65. Thus, the amplitude statistics deviate from the well-known Rayleigh distribution of c2.0, in which a logarithmic/constant false alarm rate (LOG/CFAR) circuit is useful. Therefore, it is concluded that the new Weibull/CFAR should be considered to suppress sea ice clutter.

Watermarking methods that employ orthogonal transformations are very robust against non-geometrical modifications such as lossy compression, but attaining robustness against image translation or cropping is difficult. This report describes a watermarking method that increases robustness against geometrical modifications such as image translation and cropping by embedding watermark data in the frequency component of an image and detecting that data by considering the phase difference of the coefficients that results from translation of the image. Experimental results demonstrate the robustness of this method against both non-geometrical image changes and image translation and cropping.

Using a tilted electric field (TEF) soft-landing collector, one of the authors has achieved an efficiency improvement of a TWT from 11.8 percent to 43.0 percent. However, the TEF collector requires a uniform magnetic field covering the entire collector space, and hence, a heavy magnet or electromagnet, which is far from practical in high-power tubes. This paper proposes the periodic magnetic field (PMF) soft-landing collector, which is a periodic field version of the TEF collector. It requires much lighter magnets than a TEF collector does. The principle, design theory, preliminary low-perveance experiment, and a relevant computer simulation are presented. Finally experiments with a medium-power UHF TWT equipped with a PMF collector are described.