Henning F. Harmuth – författare

Electromagnetic Signals deals with the practical applications of nonsinusoidal electromagnetic waves or carrier free radars, ultrawideband technology and large relative bandwidth technology. The book is unique since it deals with a number of current conventional radar problems along with proposed solutions.

In this text, the authors, H. Harmuth and K. Lukin, point out the deficiencies in Maxwell's theory and present a new way of obtaining transient or signals solutions. This book can be used by researchers, graduate students and scientists in the areas of physics, astrophysics, astronomy and electromagnetic theory or electromagnetics.

Most texts on electromagnetic theory follow the classical approach of steady state solutions of Maxwell's equations. In Interstellar Propagation of Electromagnetic Signals, the authors, H. Harmuth and K. Lukin, point out the deficiencies in Maxwell's theory and present an exciting new way of obtaining transient or signals solutions. This book can be used by researchers, graduate students and scientists in the areas of physics, astrophysics, astronomy and electromagnetic theory or electromagnetics.

Electromagnetic Signals deals with the practical applications of nonsinusoidal electromagnetic waves or carrier free radars, ultrawideband technology and large relative bandwidth technology. The book is unique since it deals with a number of current conventional radar problems along with proposed solutions.

The orthogonality of functions has been exploited in communications since its very beginning. Conscious and extensive use was made of it by KOTEL' NIKOV in theoretical work in 1947. Ten years later a considerable number of people were working in this field rather independently. However, little experimental use could be made of the theo­ retical results before the arrival of solid state opera­ tional amplifiers and integrated circuits. A theory of communication based on orthogonal functions could have been published many years ago. However, the only useful examples of orthogonal functions at that time were sine-cosine functions and block pulses, and this made the theory appear to be a complicated way to derive known re­ sults. It was again the advance of semiconductor techno­ logy that produced the first really new, useful example of orthogonal functions: the little-known Walsh functions. In this book emphasis is placed on the Walsh functions, since ample literature is available on sine-cosine func­ tions as well as on block pulses and pulses derived from them.

The orthogonality of functions has been exploited in communications since its very beginning. Conscious and extensive use was made of it by Kotel'nikov in theoretical work in 1947. Ten years later a considerable number of people were working in this field. However, little experimental use could be made of the theoretical results before the arrival of solid state operational amplifiers and integrated circuits. The advantages of Walsh functions, which are emphasized in this book, were recognized independently by several scientists in the early sixties. Among them were E. Gibbs, K. Henderson, F.Ohnsorg, G. Sandy and E. Vandivere, whose work was not published until many years later. Somewhat more than half the illustrations in this second edition were not contained in the first edition and this reflects the changes in contents. The most striking difference between the two editions is the progress toward practical applications made in the intervening three years. However, it may turn out that the most important change is one that appears rather theoretical on the surface and that concerns shift-invariant features strongly connected with sine-cosine functions. These functions are projections of the exponential function which, in turn, is the character group of the real numbers. The topology of the real numbers is generally accepted to be the same as that of time or a one-dimensional space, and this is the basis for a variety of claims that sinusoidal functions are unique and superior to all others.

The success of Newton's mechanic, Maxwell's electrodynamic, Einstein's theories of relativity, and quantum mechanics is a strong argument for the space-time continuum. Nevertheless, doubts have been expressed about the use of a continuum in a science squarely based on observation and measurement. An exact science requires that qualitative arguments must be reduced to quantitative statements. The observability of a continuum can be reduced from qualitative arguments to quantitative statements by means of information theory.Information theory was developed during the last decades within electrical communications, but it is almost unknown in physics. The closest approach to information theory in physics is the calculus of propositions, which has been used in books on the frontier of quantum mechanics and the general theory of relativity. Principles of information theory are discussed in this book. The ability to think readily in terms of a finite number of discrete samples is developed over many years of using information theory and digital computers, just as the ability to think readily in terms of a continuum is developed by long use of differential calculus.

Maxwell's equations have been the basis of electromagnetic theory for a century. They were very successful in providing solutions with sinusoidal time variation, but these solutions are outside the causality law and the conservation law for energy. Signal solutions, which satisfy these two laws, generally do not exist, but can be obtained by adding a term for magnetic dipole currents to Maxwell's equations. Such currents are caused by the rotation of magnetic dipoles, ranging from the hydrogen atom to the magnetic compass needle. Many computer plots of the time variation of electric and magnetic field strengths excited by signals are given in this useful book.