Date of Award

8-2017

Document Type

Thesis - Open Access

Degree Name

Master of Science in Electrical & Computer Engineering

Department

Electrical, Computer, Software, and Systems Engineering

Committee Chair

Dr. William C. Barott

First Committee Member

Dr. Brian Butka

Second Committee Member

Dr. Richard Stansbury

Abstract

A Global Positioning System (GPS) signal simulator is a valuable testing tool. It allows for testing of GPS receivers, systems, and anti-spoofing algorithms. With the increased popularity of software defined radios (SDRs) merging GPS signal simulators and SDRs is a natural choice. A detailed review of the construction of a GPS signal generator using the ROACH processing board is presented herein. The ROACH, developed by the Collaboration for Astronomy Signal Processing and Electronics Research (CASPER) team, is a processing board that can be configure to function as a SDR. In this research, the ROACH was transformed to function as a GPS signal generator able to transmit the C/A L1 civilian GPS signal. Maximum manipulation of the GPS signal was built-in to the firmware allowing the user to change the signal for different applications. Its modular architecture and ease of reproduction makes this GPS signal simulator design viable research tool in the field of GPS anti-spoofing, GPS system fabrication, and as a great GPS educational tool.

The GPS signal generator presented herein simulates the GPS C/A L1 signal at a frequency of 50.127 MHz. The generated signal contains no time delay or Doppler shift. A total of four independent GPS signals can be generated and transmitted as a single composite signal. The signal generator is capable of generating all of the current NAVSTAR defined PRN sequences allowing the simulation of any four satellite combination. It also uses the most up-to-date almanac data in the transmitted signal.

Future improvements to this GPS signal generator includes development of an up-converter to convert the transmitted signal frequency to the C/A L1 signal frequency of 1575.42 MHz, implementation of Doppler shift and time delay logic to the firmware, and software front end providing the user the ability to enter trajectory coordinates used to generate dynamic GPS signal along defined trajectory.

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