Electromagnetic waves with large relative bandwidth (Invited paper)

The history of the use of sinusoidal functions and the suitability of these functions for the transmission of information are discussed, taking into account also possibilities for a use of nonsinusoidal functions. It is shown that the available technology is capable of radiating and selectively receiving nonsinusoidal waves. As a basis for an evaluation of the application possibilities for nonsinusoidal electromagnetic waves, attention is given to a concept which makes it possible to distinguish quantitatively between theoretical sinusoidal waves, practical (almost) sinusoidal waves, and nonsinusoidal waves. A suitable measure is provided by the concept of the relative bandwidth. It is pointed out that semiconductor technology has made it possible to use radio signals with large relative bandwidth or nonsinusoidal signals, instead of conventional signals with small relative bandwidth or (almost) sinusoidal signals. The practical level of this new development was reached with the ground-probing radar. Many more applications are possible.