A Novel Geometry Multi-Stage Depressed Collector for the Efficiency Enhancement of Space Traveling Wave Tubes

A novel geometry of a multi-stage depressed collector with four stages has been designed for Ka-band space traveling wave tube. The inner structure of each electrode of the collector has been provided with a single-step corrugation of a positive slope followed by a negative slope. The performed simulation predicts that the proposed collector has 7 % more efficiency, less back streaming of electrons and lower weight as compared to the collector with conventional geometry. Additional features of this collector include inherent secondary electron trapping mechanism and better power handling capabilities. Above properties of the proposed collector makes it suitable for space applications.     

Adaptive delivery of video data over wireless and mobile environments

We present an architecture for the adaptable delivery of video data under variable connection characteristics and into devices of variable capabilities. The main application of the proposed architecture is video delivery in wireless and mobile environments. The architecture is based on the Universal Multimedia Access concept and the MPEG‐7 standard. Based on the network and the mobile device, as well as constraints imposed by user preferences and the multimedia content, video is delivered through a careful application of a combination of off‐line and on‐line reductions to the video stream. We present our architecture and describe an implementation of a system based on the architecture. We present basic performance evaluation results to quantify the merit of our approach. Copyright © 2002 John Wiley & Sons, Ltd.