Hewlett-packard Company

Kari A Santos

Christopher R Adams

Paolo L Siccardo

Albert W Kovalick

Manu Thapar

John J Youden

David John Coggins

James E Jensen

James D McVey

A video server for providing Video-On-Demand is disclosed. A plurality of data sources are coupled individually to a first and second bi-directional data/instruction switch. The first switch is additionally coupled to a data storage system and the second switch is coupled to a network interface. A real time controller is coupled to the data sources and the switches and can couple any part of the data storage system to any selected data source and any given network channel to any selected data source. A control system coupled to the real time controller and the second switch provides support services to the real time controller and acts as a gateway to third party services and products. The data storage system is largely comprised of disk drive arrays. Video data is striped across the individual arrays, each video data program that a user requests being striped across one array. Each array provides video data to many users through the data sources. The video server is tolerant of individual failures in the data storage system and among the data sources, as operating portions of the data storage system and spare data sources can be rapidly switched to substitute for failed units. The server can also be readily expanded and provides a user experience similar to that of a video cassette recorder.

Video on demand system with multiple data sources configured to provide

Method and apparatus for calibration of a vector modulator of electrical communication signals that produces an output composed of the vector sum of two modulated signals that are phase shifted relative to one another. The two output component signals are first calibrated to produce zero quadrature angle error, then compensated for carrier leakage and balanced to provide equal output amplitudes for equal data input amplitudes. Iteration of these calibrations is not necessary. The already-adjusted parameters remain calibrated as subsequent adjustments of other parameters are made.

Quadrature measurement and calibration of a vector modulator

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Palo Alto, CA, United States of America

Kari A Santos