CHARACTERISTICS OF ULTRA-WIDEBAND ELECTROMAGNETIC MISSILE GENERATED BY FOCUSED TWO-DIMENSIONAL ARRAY

Ever since the concepts of "focus waves modes" and "electromagnetic missile" were introduced in the open literature almost two decades ago, extensive research work has been carried out to arrive at physically realizable applications for such concepts. In this paper, an ultra-wideband (UWB) electromagnetic missile with the time variation of a generalized Gaussian pulse (GGP) is generated based on the principle of focused-array beamforming. The radiation pattern, or array factor, of the focused-planar array is derived, and focused-energy patterns are computed to demonstrate the decaying behavior of the radiation energy of the electromagnetic missile as a function of distance travelled from the array to an observation point. The focused-energy patterns show that the depth-of-focus, or focusing bandwidth, is directly proportional to the focusing distance, and inversely proportional to the signal frequency bandwidth and array dimension. The focusing bandwidth is a measure of how well the energy is concentrated in the vicinity of the focusing point, and it is a useful parameter for radar ranging as well as imaging. In practice, the trade-off between the focusing distance, frequency bandwidth, and array dimension for improved focusing capability (or resolution) is of interest, in particular in the case of the ground-probing radar (GPR).