This dissertation investigates the use of digital and adaptive beamforming techniques for remote sensing applications. While the theoretical foundations for digital and adaptive beamforming are well established, the application of these results to remote sensing imaging radar has seen little development in the literature. Practical radar systems suffer from a variety of component errors and simple logistical issues that complicate the direct application of theoretical results. The objective of this work is to investigate the limitations of the current theory, and to demonstrate the practical application of the theory where possible.
Antenna hardware is a critical component in a digital beamforming system and the first part of this thesis details the design, fabrication, and testing of the antenna hardware for the Turbulent Eddy Profiler (TEP) radar system. A corrugated pyramidal horn antenna serves as the high power transmit horn, and a printed microstrip antenna is used as an element in a ninety-one element receive array. Detailed design procedures are given for both transmit and receive antennas, and a complete set of machine drawings are included. The antennas were fully tested, and measured results are given for the transmit antenna, a single receive element, and a seven element array.
The second major section of this dissertation introduces digital and adaptive array processing principles, and investigates the impact of common system errors on the capabilities of these systems. A unified treatment of system errors is presented, and individual error sources are examined in terms of their impact on important performance indexes. A new result is obtained relating the achievable null depth to the cross-correlation terms of the array's correlation matrix.
The final section of this dissertation examines the practical application of digital and adaptive beamforming theory to remote sensing imaging radar. Computer simulations and experimental data are used to demonstrate the application of theoretical results to signal environments typical of remote sensing radars. Limitations on antenna performance derived from the theory are discussed, and suboptimal array processing architectures are considered. Experimental results from the FOPAIR (linear array) and TEP (planar array) systems, both developed by MIRSL, form the basis of this section.
