Analytical model for the HPEM radiation from helical antennas

Axial radiation from a helical antenna looks somewhat like a damped sinusoid in time domain, with some important distinction. It has been observed that the radiated waveform initially grows in time and then starts to decay. Consequently a simple damped sinusoidal model for the radiated field is inadequate. In this paper, we cite some examples of the observed radiation from helical antennas and offer an analytical model that well explains the behavior of helical antennas.