Some Characteristics of Planar Distributed Sources for Radiating Transient Puises

This note considers some of the characteristics of a planar distributed source for radiating a pulse -in a narrow beam to large distances. Two cases are considered. In the first case (toward which most of the discussion is aimed) the distributed source is used to radiate a pulse which has a single polarity after the initial rise out to as large a time as possible; as a radiated pulse from a finite size source with finite energy the waveform must eventually change polarity (for a given field component) . Considering the case of a spherically expanding wave, a lower bound for the unipolar pulse width is established based on the radius of curvature of the wavefront and the size of the source array. Then the height of the array above the ground is considered for its effect in limiting the unipolar pulse width. In the second case the distributed source is discussed from the viewpoint of radiating a pulsed CW waveform because of the gains associated with focusing the fields at desired positions in space. In this note most of the discussion is qualitative, pointing out many of the potential features of such arrays. Detailed quantitative investigations are left to future notes. BUWEDFL)RPALIC RELEASE ... . s,. _-= . ----. . . . ~. ..--,