Volume 4, Number 1

4-1 cover

Wafer-Scale lntegration of a Large Systolic Array for Adaptive Nulling
C.M. Rader

This article describes an architecture for a highly parallel system of processors that are specialized for real-time adaptive antenna nulling computations with many degrees of freedom. This system is called the Matrix Update Systolic Experiment (MUSE), and we describe a specific realization of MUSE for 64 degrees of freedom. Each processor uses the Coordinate Rotation Digital Computation (CORDIC) algorithm and has been designed as a single integrated circuit. Ninety-six such processors working together can update the 64-element nulling weights on the basis of 300 new observations in only 6.7 ms. This update rate would require 2.88 billion instructions per second from a conventional processor. The computations support 50 dB of signal-to-interference ratio (SINR) improvement in a sidelobe canceler. The simple connectivity between processors permits MUSE to be realized on a single large wafer by using restructurable VLSI.

High-Speed Optical Interconnections for Digital Systems
D.Z. Tsang

As an alternative to electrical interconnections, optical interconnections are being investigated for digital systems that require high speed, density, and connectivity. In particular, diode-laser-based optical interconnections with high optoelectronic conversion efficiencies promise simple interconnections that can operate even at gigahertz rates. Optical modules in which critical alignments have been performed during module assembly can reduce module placement requirements from micrometers to millimeters. Such modules can also eliminate the need for micropositioners in digital systems. This article describes the basic concepts of optical interconnections, the progress on experimental diode-laser-based free-space optical interconnections, and the future prospects for this technology.

Techniques for Information Retrieval from Speech Messages
R.C. Rose

The goal in speech-message information retrieval is to categorize an input speech utterance according to a predefined notion of a topic, or message class. The components of a speech-message information-retrieval system include an acoustic front end that provides an incomplete transcription of a spoken message, and a message classifier that interprets the incomplete transcription and classifies the message according to message category. The techniques and experiments described in this paper concern the integration of these components, and represent the first demonstration of a complete system that accepts speech messages as input and produces an estimated message class as output. The promising results obtained in information retrieval on conversational speech messages demonstrate the feasibility of the technology.

The Development, Variations, and Applications of an EHF Dual-Band Feed
J.C. Lee

A compact, high-performance, EHF dual-band feed has been designed and developed. Subsequent improvements and modifications for a wide range of antenna applications have been made.

This article begins with three working examples of existing dual-band-antenna approaches, and discusses the dual-band feed that was developed for the antenna to be used on the SCOTT ADM, a satellite communications terminal for mobile command posts. Excellent performance for the feed and antenna in both bands has been achieved. Other applications of the feed with appropriate modifications for dielectric-lens antennas, ADE (displaced-axis elliptical) antennas, and compact eletronic-lobing antennas are also discussed. These variations of feeds have been used in the FEP spot-beam antenna backup and a military-communications-satellite spot-beam antenna, in satellite-communications terminals on submarines, and in portable terminals (e.g., SCAMP and Advanced SCAMP).

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