Date of Award

3-21-2013

Document Type

Thesis

Degree Name

Master of Science

Department

Department of Electrical and Computer Engineering

First Advisor

Geoffrey Akers, PhD.

Abstract

Aircraft based direction finding (DF) in the high frequency (HF) band is difficult due to the aircraft's size with respect to wavelength and limited azimuthal resolution. A B-dot sensor is useful for detection of the time varying magnetic field and offers improved integration into an aircraft. What the B-dot sensor gains in integration it gives up in sensitivity because it is designed for frequencies above 5 GHz. Design of an airborne HFDF array using Bdot sensors is based in maximizing the physical extent of the array and eliminating multiple main beams. The goals of this research are to complete a computational analysis of a B-dot sensor, evaluate a cluster of closely spaced B-dot sensors, and design an array of B-dot sensor clusters on a simulated airborne HFDF platform. The B-dot sensors are simulated to determine the sensitivity of the sensor and sensor cluster. Eight and ten-sensor elements are placed on a simulated airframe to characterize the direction finding capability in the HF band. Additionally, a field test is accomplished to compare the simulated B-dot sensor cluster to an actual cluster of Bdot sensors. The B-dot sensor is inadequate for use in an HFDF array due to a lack of sensitivity, but based on initial simulations a larger B-dot sensor, designed for 700 MHz, offers equivalent sensitivity to previous research. Utilizing a cluster of sensors improves the radiation efficiency by 6 dB. The eight and ten-element arrays offer a limited direction finding capability due limited sidelobe reduction. The addition of two sensors does present sidelobe reduction; therefore, additional sensors will improve the direction finding capability of the airborne HFDF array.

AFIT Designator

AFIT-ENG-13-M-02

DTIC Accession Number

ADA577289

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