Date of Award


Document Type


Degree Name

Doctor of Philosophy (PhD)


Electrical and Computer Engineering

Committee Chair

Laurie L. Joiner

Committee Member

Adam Panagos

Committee Member

Yuri Shtessel

Committee Member

Maria Pour

Committee Member

Sivaguru Ravindran


Global Positioning System., Antennas (Electronics), Simulation methods.


The need to test and evaluate adaptive nulling technology for Global Navigation Satellite System (GNSS) receivers is increasing commensurately with the demand for additional protection against GNSS interference. Because the cost and time associated with approval to conduct optimum outdoor testing is often prohibitive and safety of flight concerns arise during integration testing as well, affordable and accurate means of simulated testing are desired. This dissertation investigates the theory and implementation of Radio Frequency (RF) wavefront simulation that eliminates expensive RF front-end electronics, as well as other active components that limit dynamic range, add exogenous noise, and restrict maximum power capabilities. The method employs mechanical tap-delay lines as the core component of the wavefront simulation that provides many benefits in calibration, cost, and precision RF phase delay. The novel theory presented in this dissertation quantifies a truth estimate for the discrete mechanical tap-delay performance through an a priori mapping of the per-channel phase error, while minimizing the hardware limitations. A main focal point of the research and theory developed is to answer the question, "what is truth?" The accuracy and repeatability of hardware undergoing evaluation is compared to truth to determine the usefulness of the solution. Therefore, it is critical to understand what truth is in a simulation environment. However, there is not a straightforward answer when there are known errors affecting the ability of the simulation to create a valid RF wavefront environment. A proposed solution to define a truth estimate that applies novel analysis techniques to understand the effect of per-element RF phase error at a system level is presented. The concept, which is described in detail in the dissertation, defines a discrepancy between a strict truth estimate using a Steiner tree model, and a loose truth estimate using the well-known MUlitiple SIgnal Classifcation (MUSIC) algorithm. A valid region exists when the discrepancy remains within the observability of the system under test. In essence, this method bounds the error and serves to define the valid regions for the RF wavefront environment. An enhanced tap selection method is also described that increases the available angle of arrival possibilities that fall within the criteria for being valid. This creates an enhanced capability that uses theory and concepts from engineering and mathematics to overcome hardware limitations.



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