Transient radiation of a single-cycle sinusoidal pulse from a thin dipole

Abstract

The behavior of the radiated electric field from a half-wave dipole in free space excited by a single-cycle sinusoidal voltage is studied. The zero-order approximate solution for the current along the antenna in the frequency domain is used, so that the time-dependent current as well as the radiated electric field can be calculated and interpreted easily. Under a suitable matched condition, the time dependent current along each half-section of the dipole is made up of a current pulse traveling from the feed-point and a reflected one from the end-point. However, the radiated electric field consists of five overlapping signals exhibiting that radiation takes place only from the discontinuities of the dipole antenna. Both current and the radiated electric field are extended in time due to the reflection of current from the end-points of the dipole antenna. It appears that the spectral bandwidth of the radiated electric field is narrower than that of the exciting voltage pulse. This phenomenon may be due to the filtering effect of the half-wave dipole.