On prediction of the asymmetry resonance phenomenon of log-periodic dipole antennas

The asymmetry resonance phenomenon of log-periodic dipole antennas is analyzed using the moment method. Relevant plane-wave, far-field scattering computations are presented for a parallel-wire resonator, a single cell of a log-periodic dipole antenna and a complete antenna. Also, moment-method computations are presented for the gain of a generator-driven log-periodic dipole antenna. The computations are compared with published experimental results and it is concluded that the asymmetry resonance phenomenon can be predicted by a theory which allows for both unbalanced currents on the antenna feeder and radiation from the feeder. It is recommended that this phenomenon be given serious consideration in the design of any high-performance log-periodic dipole antenna.