Design, Modeling, and Testing of Microstrip Patch Antenna Arrays for Vertical Takeoff & Landing Aircraft
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A major shortcoming of aircraft antennas for autonomous landing systems is the acquisition and tracking errors resulting because of the illumination of the airframe components by the 360° azimuth beamwidth of a low gain omni-directional antenna. Also, existing low and high gain antennas currently found in the marketplace are both expensive and time-consuming to manufacture. The purpose of this thesis is twofold: to develop a low gain omni-directional antenna that radiates only in the forward direction and to develop a high gain antenna that is less expensive compared to antennas currently found in landing systems. Microstrip patch antenna arrays are selected due to their light weight and low cost. The design, numerical modeling, and experimental characterization of two types of microstrip patch antenna arrays are described. CST's Microwave Studio, a three-dimensional electromagnetic simulator, is used to model, simulate, and optimize the performance of the antennas. The antennas have been fabricated and the return loss and radiation patterns were measured. Return loss comparisons between the simulated and measured antennas show a difference of nearly 500 MHz in the resonance frequency for both the low and high gain arrays. Simulated and measured peak directivities differ by as much as 1.7 dB. These differences between the simulated and measured results are believed to be caused by manufacturing tolerance uncertainties as well as by some design details that were intentionally not accounted for in the modeled antennas.