Behavior of Very Large Short Pulse Antennas. Revision 1

摘要

The electromagnetic behavior of a pulsed array of radiating elements can exhibit marked differences from standard continuous wave (CW) behavior when the physical size of the array, D, exceeds the physical pulse length, cT (speed of light times pulse duration). Herein we present a simple analytical model and the results of computer code calculations which explain and illustrate those differences. We further elaborate on the behavior of these very large transient antennas (VLTA) by using computer codes to illustrate the effects on the radiation pattern when the radiators exhibit randomness of turn-on time, phase, or amplitude. Our results show that the physical space into which a linear VLTA radiates can significantly be divided into two regions by the off-axis angle THETA/sub T/ identical to arcsin (cT/D). Within the near-axis region (THETA < THETA/sub T/), the behavior of a coherently radiating (pulses simultaneously initiated) array is dominated by a CW antenna pattern. That is, the lobe structure found in the energy-deposition pattern is essentially that of the CW case. In the far-axis region (THETA > THETA/sub T) the behavior of a coherently radiating array is dominated by transient effects. No CW-like pattern is seen; instead the energy-deposition pattern is roughly proportional to 1/sin exp 2 THETA with only a suggestion of lobes. (ERA citation 11:007636)