Date of Award

Spring 1962

Document Type

Thesis - Restricted

Degree Name

Master of Science (MS)


Electrical Engineering

First Advisor

Ishii, Thomas K.

Second Advisor

Horgan, James D.

Third Advisor

Moeller, Arthur C.


In the first section of the thesis, a theoretical derivation is made of bandwidth as a function of resonant frequency of a single crystal ferrite isolator at 58 kMc. The derivation takes into account the ferrite isolator as a bounded system. Using this relation, equations are derived which relate line width to resonant frequency, line width to bandwidth, and line width to applied field. It was possible to fit these equations to experimental data obtained with a single crystal barium ferrite. The equations indicated almost linear relationships between bandwidth and resonant frequency, line width and resonant frequency, and line width and bandwidth for a 1 kMc frequency range. The remainder of the thesis describes experimental design work with tow different ferrite materials, titanium substituted barium ferrite and aluminum substituted strontium ferrite. The titanium substituted barium ferrite requires a 5000 gauss external field for isolator operation while the alumium substituted strontium ferrite is capable of isolator operation without an external field. Experimental work showed that isolator performance was improved by increasing the length of the ferrite strips, by increasing the thickness of the ferrite strip, and by dielectric loading of the ferrite strip. Isolator performance deteriorated by reducing the height of the ferrite, increasing the thickness of the ferrite beyond a certain limit, and mounting the ferrite too far out into the waveguide. The internal field of the barium ferrite appeared to be more stable with time than that of the strontium ferrite, probably because the internal field was stabilized by the biasing magnets. These results enabled usable laboratory isolators to be built, using both the substituted barium ferrite and the strontium ferrite. The best result was an externally biased isolator that has a 22 db backward loss and a 2db forward loss over a 7 kMc bandwidth from 53 to 60 kMc. This fixed field bandwidth is much wider than any commercially available Faraday rotation isolators at these frequencies.

Fifth Advisor




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