Date of Award

Summer 2000

Document Type

Thesis - Restricted

Degree Name

Master of Science (MS)

Department

Electrical and Computer Engineering

First Advisor

Richie, James

Second Advisor

Jeutter, Dean

Third Advisor

Wolski, Mark

Abstract

The antenna characteristics and effectiveness of radio signal propagation from an aircraft are often influenced by large overhead rotating members, such as helicopter blades, which leads to degradation in performance. This thesis discusses high frequency (HF) antenna characteristics on a large cargo transport helicopter and the signal modulation effects caused by helicopter blade rotation. Antenna gain and signal fluctuation in the near vertical direction from the helicopter are considered for the normal radio frequency (RF) propagation mode. Various antenna configurations are reviewed using simulation and modeling in an effort to improve overall gain and reduce the amount of fluctuation. Antenna performance and dependence with blade rotation and frequency variation are reviewed. An insight into the electromagnetic fields present on the simulated helicopter is offered in an attempt to understand the gain and modulation effects for the various antenna configurations. The dependence of the radiated fields on the size and geometry of the antenna and helicopter is discussed. Ideas for improving signal gain using different antenna configurations and geometry are presented. The Chinook CH-47 helicopter and HF radio communication system provides a basis throughout this thesis for analyzing and understanding the rotor modulation effects. The analysis, ideas, and results may also apply to other helicopter communication systems.

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