Ultrawide band active radar array antenna for unmanned air vehicles

The development of highly efficient, optically activated, semiconductor switches will yield compact radar transmitters that can be applied to airborne surveillance missions on unmanned air vehicles. Radar systems employing these high peak power sources must use ultrawide band antenna elements to efficiently meet system performance requirements. Unfortunately nearly all antenna elements that can meet the bandwidth requirements are undesirable for the airborne application because of their geometry and orientation necessary to utilize the maximum directivity. The equiangular spiral is a planar element which is suitable for the airborne application. This paper presents a heuristically derived expression for the transient radiation from this antenna and examines the performance of an ultrawide band active array composed of equiangular spiral elements, including beam forming and compensation of the waveform dispersion introduced by the spiral