IMPROVED CURRENT DECOMPOSITION IN HELICAL ANTENNAS USING THE ESPRIT ALGORITHM

We apply the ESPRIT algorithm to decompose the currents on a helical antenna into difierent traveling wave modes. The strengths, phase velocities and decay constants of the various modes are extracted across frequencies. Their contributions to the antenna performance including gain, polarization and time-domain radiated pulse shape are investigated. Our results show that the T + 0 mode is a dominant contributor to the helix gain at the low end of the frequency band while the T + 1 mode contributes signiflcantly to the gain at higher frequencies. It is also found that the re∞ected current modes from the open end reduce the circular polarization purity of the helix. Lastly, it is observed that the T + 1 and T + 0 modes contribute constructively to a low-dispersion pulse from the antenna.