Date of Award

Summer 2000

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Electrical & Computer Engineering

Program/Concentration

Electrical Engineering

Committee Director

Charles F. Bunting

Committee Member

Linda L. Vahala

Committee Member

Ravindra P. Joshi

Call Number for Print

Special Collections LD4331.E55 S34

Abstract

Mode stirred chambers are used to perform radiated susceptibility tests on equipment that is expected to operate normally when exposed to electromagnetic (EM) fields. These tests are useful in identifying failure events in airborne equipment and other electronic equipment that are exposed to EM fields. This thesis is focused on further defining the operating environment of mode stirred chambers and relating the electromagnetic environment in the chamber to the electromagnetic environment of an actual aircraft. The majority of mode stirred chamber tests are implemented by using mechanical mode stirring. Mechanical mode stirring is the process of varying boundary conditions in a complex cavity to cause the redistribution of the modal structure in the cavity. As the field structure is redistributed, the changing amplitude and phase of the fields could expose a device under test to additional frequency content. In order to ensure that devices under test are only susceptible to the intended test frequency, a characterization of the additional frequency content due to the mechanical mode stirrer is required. A rigorous definition of the phenomena associated with mode stirring will be presented along with an analysis of the frequency content associated with mechanical mode stirring.

In February 1995, a flight test was conducted on NASA's Boeing 757 aircraft. The aircraft was flown with an electromagnetic data acquisition system on board, which was used to measure the external and internal electromagnetic environment of the aircraft. The electric field was recorded as the NASA 757 was flown past sources in the HF, VHF, UHF, and C-band frequency ranges. This thesis examines the statistics of the UHF data from the flight test. The comparison of the flight test data to the theoretical probability density function describing the electric field in the mode stirred chamber is unique. This comparison provides a strong means of relating the electromagnetic environment in the chamber to the electromagnetic environment of an actual aircraft.

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DOI

10.25777/ah5v-t624

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