Comparison of coaxial dipole antennas for applications in the near-field and far-field regions

Coaxial antennas with properties similar to those of a two-wire dipole antenna are presented and analyzed. Since coaxial antennas extend along a straight line and can have almost any radius, they may be easily inserted into confined spaces that require an antenna. Coaxial antennas are easy to construct, naturally adapted to a coaxial input connection, thus avoiding the use of a balun (a balanced to unbalanced adapter), and avoid using a T-shaped structure (as for the two-wire dipole). By altering in specific ways the inner and outer conductors of a 50 Ω transmission line, four different coaxial antennas are formed that have characteristics similar to those of a two-wire dipole antenna. These antennas are compared and discussed, while noting the similarities and differences between them and the two-wire dipole antenna. The antenna parameters determined are the near-field and far-field radiation patterns, the input impedance and the input reflection coefficient (S 11). The antennas are modeled using a high frequency structure simulator (HFSS), then constructed and their properties measured to confirm the calculations and simulations.

Duke Scholars

Author William T. Joines Pierre R. Lamond Department of Electrical and Computer Engin ...