Date of Award

5-2006

Degree Type

Report

Degree Name

Master of Science (MS)

Department

Electrical and Computer Engineering

Committee Chair(s)

Charles Swenson

Committee

Charles Swenson

Committee

Annette Bunker

Committee

Paul Israelsen

Abstract

The Plasma Impedance Probe (PIP) electronics board is designed to measure the impedance of plasma in situ by emitting voltages at different frequencies from a probe. The PIP is launched as part of the Tropical Storm mission. The purpose of the mission is to launch the instrument aboard a sounding rocket that flies through the ionosphere during or immediately following a large tropical meteorological disturbance. As the PIP probe travels through the upper regions of Earth's atmosphere, data are gathered from the disturbed region by measuring the current flow in the antenna. This information contains both the phase and magnitude information of the plasma. The data are sampled by Analog-to-Digital Converters and read into an FPGA. With these measurements, the impedance of the plasma is calculated. The data gathered from the PIP increases the knowledge of certain phenomena inherent to communication through the ionosphere, particularly following large terrestrial disturbances.

The digital portion of the PIP circuit board provides several features. First, it facilitates quadrature sampling by providing the proper timing of the Direct Digital Synthesis (DDS) chips, synchronizing the analog portion of the design with the digital. Second, the digital component samples the data at appropriate intervals while providing an interface with the telemetry system. Third, through a series of data operations and preprogrammed calibration data, the FPGA tracks the resonating frequency of the plasma. The complex data operations include the linear interpolation of calibration data gathered to account for the delays inherent in the system at different frequencies. Also included in the operations is a digital implementation of the arctangent function and a pipelined divider. Finally, the digital component allows the instrument to be calibrated by providing an interface with a common PC using LabVIEW.

A top down, bottom up approach is used in the fabrication of the PIP digital component. This report documents the details of the PIP digital design, shows how it effectively meets the requirements determined by the analog design, and displays the results of the calibration process.

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