The characteristics and design of the conical log-spiral antenna

The balanced conical logarithmic-spiral antenna is considered as a slow-wave locally periodic structure with a slowly varying period. A study of the near fields and their relationship to the far fields has led to the identification of the active region or effective radiating aperture on the antenna and to a clearer understanding of its operating characteristics. Information of the near- and far-field characteristics and on the input impedance for a wide range of parameters is presented in a form suitable for use in the design of practical antennas.