AbstractsEngineering

Typewritten MS. Examination of the widely-accepted statement that signals weaker than thermal noise are useless shows it to be inadequate. By definition of information transfer in terms of probability theory, and application of Bayes' Theorem, a new general formula for the information which can be received in a given bandwidth and time in the presence of any amount of noise is obtained. Some special cases and deductions follow, one of which is that signals weaker than thermal noise are not useless. Consideration is given to the design of a weak-signal detector, operating on changes of distribution produced in some property of the noise by the presence of signals. Experimental operation of such a statistical detector is roported for signal-to-noise ratios of less than one. Early papers on radio noise are discussed briefly: the bibliography is .extensive. Improvement of maximum radar ranges on small targets is suggested among the problems for further research.