Date of Award:

5-1988

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Electrical and Computer Engineering

Committee Chair(s)

Kay D. Baker

Committee

Kay D. Baker

Committee

L. Carl Howlett

Committee

Don Lind

Abstract

A unique wide-range voltage-controlled oscillator (VCO) has been part of the plasma frequency probe (PFP) for many years. The uniqueness of this VCO is how it is tuned with an electronic tuneable inductor in conjunction with a varactor diode. Though the PFP has been utilized successfully for rocketborne ionospheric electron density measurements, fine resolution data was limited by strange frequency jumps (approximately 5 percent uncertainty in electron density) which have appeared in flight results. This thesis examines the cause of some of these jumps, and shows they are instrument related and more particularly caused by the ferrite tank inductor core of the VCO. Investigation was also centered on improving the performance of the VCO, enabling it to respond to faster changes of electron density in the ionosphere. As a consequence of this investigation, methods of extending the maximum operating frequency of the ferrite tank inductor were found which make possible the use of high permeability ferrites in the VCO. By incorporating a new VCO free from frequency jumps with better linearity and speed along with improvements to RF circuitry, results show a new PFP with performance that is markedly improved with respect to accuracy, speed, and reliability.

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332d0981f94bf4f89aa03358a2c8f81c

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