Engineering Commons^™

Unit Circle Roots Based Sensor Array Signal Processing, Jared P. Smith

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As technology continues to rapidly evolve, the presence of sensor arrays and the algorithms processing the data they generate take an ever-increasing role in modern human life. From remote sensing to wireless communications, the importance of sensor signal processing cannot be understated. Capon's pioneering work on minimum variance distortionless response (MVDR) beamforming forms the basis of many modern sensor array signal processing (SASP) algorithms. In 2004, Steinhardt and Guerci proved that the roots of the polynomial corresponding to the optimal MVDR beamformer must lie on the unit circle, but this result was limited to only the MVDR. This dissertation contains …

Leveraging 3d Models For Sar-Based Navigation In Gps-Denied Environments, Zachary A. Reid

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This thesis considers the use of synthetic aperture radar (SAR) to provide absolute platform position information in scenarios where GPS signals may be degraded, jammed, or spoofed. Two algorithms are presented, and both leverage known 3D ground structure in an area of interest, e.g. provided by LIDAR data, to provide georeferenced position information to airborne SAR platforms. The first approach is based on the wide-aperture layover properties of elevated reflectors, while the second approach is based on correlating backprojected imagery with digital elevation imagery. Both of these approaches constitute the system we have designated: SARNAV. Building on 3D backprojection, localization …

Impact Of Near-Field-To-Far-Field Transformation On Sar Images Formed In An Indoor Non-Anechoic Environment, Jacob D. Compaleo

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This work investigates the impact of the near-field-to-far-field transformation (NFFFT) algorithm on phase history measurement collections completed in the Sensors and Signals Exploitation Laboratory (SSEL). SSEL is an indoor non-anechoic environ- ment that is at risk to some measurement interferences such as multiple bounces. Complete 360-degree phase history measurements of scale model aircraft are con- ducted at varying range values within the near-field limit. These measurements are calibrated with the Mie series scattering solution for a sphere. After calibration, the measurements are transformed using the NFFFT, with radar cross-section (RCS) estimated. RCS of the transformed data is compared with the …

Chaotic Based Self-Synchronization For Rf Steganography Radar/Communication Waveform, Michael A. Gonnella

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In this project, we continue previous CSR project entitled RF Steganography based Joint Radar/Communication Waveform Design to develop a bio-inspired secure low probability detection (LPD) radio frequency (RF) waveform that can serve multiple purposes simultaneously. Previously, we have developed an RF steganography based RF waveform to conceal a secure digital communication within a linear frequency modulated (LFM) chirp radar signal. By exploiting novel reduced phase shift keying modulation and variable symbol duration, the new waveform is resistant to time domain analysis, frequency domain analysis and cyclostationary analysis. However, to demodulate the hidden communication message, the intended receiver has to know …

Modular Multi-Signal Tracking Pulse Descriptor Word (Pdw) Generator With Field Programmable Gate Array (Fpga) Implementation, Justin Darrell Pelan

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As signal spectra become dense, the task of tracking and identifying radars becomes increasingly cumbersome. The variety of radars in modern theaters of war compound the task due to simultaneous operation. Real-time processing of large data sets prove difficult for sequential systems, and the parallelism of Field Programmable Gate Arrays (FPGAs) becomes an attractive option. To mitigate the increasing complexity of this task, this design proposes an FPGA architecture to produce pulse descriptor words (PDW) for up to eight independent radio frequency signals that can be used in near-real-time processing. Focusing on digital hardware techniques and modular design allow for …

Multi-Carrier Radar For Target Detection And Communications, John David Ellinger

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This dissertation considers the optimization of radar performance within the structure imposed by a coded Orthogonal Frequency Division Multiplexing (OFDM) format required to achieve an acceptable communication link. The dual goal of achieving both satisfactory radar and communication performance raises challenges that can be substantively addressed by combining phase coding and modulation techniques to provide the temporal and spectral structure necessary to implement simultaneous radar and communication operations. In particular, the specific techniques, as introduced within this dissertation, of using the Multi-Frequency Complementary Phase Coded (MCPC) sequences, as prescribed by Levanon and Mozeson, for simultaneous radar and wireless communication operations …

Performance Prediction Of Constrained Waveform Design For Adaptive Radar, Aaron M. Jones

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Today's radars face an ever increasingly complex operational environment, intensified by the numerous types of mission/modes, number and type of targets, non-homogenous clutter and active interferers in the scene. Thus, the ability to adapt ones transmit waveform, to optimally suit the needs for a particular radar tasking and environment, becomes mandatory. This requirement brings with it a host of challenges to implement including the basic decision of what to transmit. In this dissertation, we discuss six original contributions, including the development of performance prediction models for constrained radar waveforms, that aid in the decision making process of an adaptive radar …

Large Scene Sar Image Formation, Leroy A. Gorham

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With new advances in digital signal processing technology, Synthetic Aperture Radar (SAR) systems are capable of collecting high resolution data over very large scenes. Well known image formation algorithms such as the polar format algorithm (PFA) create image artifacts in large images due to phase errors introduced by the algorithm. In this dissertation, we analyze the nature of these artifacts by comparing PFA to an exact imaging algorithm, the backprojection algorithm (BPA). First, we perform a novel phase error analysis by decomposing the PFA phase errors into constant, linear, and quadratic terms for arbitrary flight paths. Second, we utilize the …

Modern Digital Chirp Receiver: Theory, Design And System Integration, Stephen Ray Benson

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Chirp signals can achieve a high range resolution without sacrificing SNR or maximum range, making them a strong candidate for use in radar and sonar applications. Chirp signals are also power efficient and resistant to interference, making them well suited for communication applications as well. The proposed digital high chirp rate receivers will showcase the use of digital instantaneous frequency measurement (IFM) devices for high chirp rate measurement. The receivers are paired with a high resolution time-of-arrival algorithm, capable of detecting the TOA and TOD of a pulse with an average error of less than 2ns. The high resolution pulse …

Frequency Modulated Continuous Wave Radar And Video Fusion For Simultaneous Localization And Mapping, Andrew Stephen Kondrath

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There has been a push recently to develop technology to enable the use of UAVs in GPS-denied environments. As UAVs become smaller, there is a need to reduce the number and sizes of sensor systems on board. A video camera on a UAV can serve multiple purposes. It can return imagery for processing by human users. The highly accurate bearing information provided by video makes it a useful tool to be incorporated into a navigation and tracking system. Radars can provide information about the types of objects in a scene and can operate in adverse weather conditions. The range and …

Performance Analysis Of Radar Waveforms For Congested Spectrums, Shaun W. Frost

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With more users populating the RF spectrum and hence less available contiguous bandwidth, radar and communication waveforms are slowly forced to become more efficient at using their available frequencies. Two scenarios are considered: operation in a colored interference environment and operation in discontiguous spectral bands. Unconstrained algorithms for designing transmit waveforms and receive filters are evaluated, wherein varying a convex weight trades performance between spectral flatness and side lobe levels. An empirical study provides performance bounds for constrained radar waveform designs for an instantiation of the interference spectrum.

Closed-form predictions for integrated sidelobe ratio (ISLR) and peak-to-sidelobe ratio (PSLR) for …

Human Micro-Range/Micro-Doppler Signature Extraction, Association, And Statistical Characterization For High-Resolution Radar, Orelle Ryan Fogle

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Recently, the use of micro-Doppler (μD) radar signatures for classification has become an area of focus, in particular for the case of dynamic targets where many components are interacting over time. To fully exploit the signature information, individual scattering centers may be extracted and associated over the full target observation. Due to the complexity of the target signature, the automated analysis is very difficult. However, the availability of ultra-fine resolution or micro-range (μR) resolution along with target scattering knowledge, can aid this process immensely. Here, we describe a feature extraction algorithm which utilizes both μD and …

Frequency Diverse Array Receiver Architectures, Aaron M. Jones

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Typical radar systems are limited to energy distribution characteristics that are range independent. However, operators are generally interested in obtaining information at particular ranges and discarding elsewhere. It seems appropriate then to attempt to put energy solely at the range(s) of interest, thus minimizing exposure to clutter, jammers and other range-dependent interferences sources. The frequency diverse array (FDA) can provide a mechanism to achieve range-dependent beamforming and the spatial energy distribution properties are investigated on transmit and receive for different architectures herein.

While simplified FDA receive architectures have been explored, they exclude the return signals from transmitters that are not …

A Study Of The Impact Of Hardware Design Choices On The System Impulse Response Of A Signal-Level Radar Simulation, Kelly Renee Feirstine

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The main goal of this research is to study the effect of hardware design choices at the signal-level of an end-to-end radar system. An implementation of waveform diversity concepts, or the use of various waveforms in both transmit and receive is employed. An end-to-end Matlab simulation is developed such that the system impulse response to hardware imperfections and waveform parameters such as bandwidth and frequency channel spacing can be analyzed. Multiple frequency channels as well as multiple pulses are also considered in the research.

All hardware components are nonlinear to some degree. The nonlinearities of the hardware give rise to …