Very Broad Band VHF/UHF (Very High Frequency/Ultra High Frequency) Omnidirectional Antenna Design Study.

摘要

This investigation examines a number of broadband VHF/UHF antennas with respect to their suitability for a small pilotless air vehicle (A/V). Specifically, the objective of this research was to find a vertically polarized omnidirectional VHF/UHF antenna having a bandwidth of at least 4:1, and whose dimensions are compatible with the size limitations of a small A/V. This investigation includes an extensive literature review, a computer analysis of a modified log-periodic dipole array, and an analysis of a number of thin-wire open-sleeve dipole antennas. The objective of the open-sleeve dipole analysis was to determine how the impedance bandwidth can be broadened by adjusting sleeve length, sleeve spacing, and transmission line impedance. Results indicate that the thin wire open-sleeve antenna can, theoretically, attain a 3.6:1 bandwidth for a VSWR of 3.0:1 or a 1.6:1 bandwidth for a 2.0:1 VSWR. Theses. (rrh)