Lecture Series on Propagation Limitations for Systems Using Band- Spreading. Papers Presented in Issy-les-Moulineaux on 7-8 June 1990; Rome Italy on 11-12 Jun 1990; and Hanscom AFB, Massachusetts on 19-20 June 1990
Abstract
The safety and the quality of transmissions have always been a matter of concern for radio operators. As radio communications began, users soon recognized that noise was a disturbing factor against which it was necessary to provide protection. Reduction of the bandwidth of the modulated signal appeared as a natural solution but, unfortunately, it could not definitely improve transmission efficiency. Discovery of frequency modulation, and the development of information theory pointed out the gain which could be expected by extending the spectrum of modulated signals. When applied to perfect communication channels, spread spectrum seems to have no limitations. With real channels, the attainable spreads are limited by numerous phenomena which distort the transfer functions. This Lecture Series is devoted to the study of these phenomena and to the consequences they have on signal transmission. Presentation of the topics takes into account both the atmosphere areas wherein the phenomena appear, and the working frequency, since the effects are always selective. The lectures begin with a general discussion of noise and interference problems, of distortions, and of characterization of the transfer functions of communication channels. Then the physical phenomena involved in the propagation of radio waves are investigated, and their effects on the various types of modern communication systems are developed.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 01, 1991
- Accession Number
- ADA239924
Entities
Organizations
- AGARD