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Hopkins, Nicholas ChristianComparative Analysis of ISAR and Tomographic Radar Imaging at W-Band Frequencies
Master of Science (M.S.), University of Dayton, 2017, Electrical and Computer Engineering
As radar technology development advances and more devices are employed in traditional frequency allocation bands, such as the microwave portion of the frequency spectrum, users are increasingly struggling to operate amidst this spectrum congestion. With spectrum congestion on the rise, application performance degradation is progressively being realized due to scarce available bandwidth. Therefore, users, such as the 5G wireless community and the automotive industry, are exploring applications at higher portions of the frequency spectrum with such efforts being focused in the millimeter wave (MMW) frequency bands. A number of novel applications, such as full-body imaging and automotive collision avoidance systems, have been improved on or realized with the aid of MMW frequencies and their associated phenomenology. However, this portion of the spectrum lags, in some cases by orders of magnitude, far behind in research and development in comparison to other bands such as those found in the microwave region. Therefore, a clear need to aid the knowledge base and investigate MMW radar phenomenology has been undertaken in this thesis. The research this thesis documents concerns designing, building and, fielding a distributed aperture array W-band (MMW) radar system. This thesis details incrementing the current fielded radar system capability from mono-static to bi-static imaging configurations. An improved method for calibrating the radar system resulting in higher quality imagery is also documented. The defined radar system was designed with the goal of performing multi-static Tomographic imaging. The research covered in this thesis is the first step toward incrementing the fielded system to full maturity.

Committee:

Michael Wicks (Committee Chair); Lorenzo Lo Monte (Committee Member); Howard Evans (Committee Member); Robert Penno (Committee Member); Andrew Bogle (Committee Member)

Subjects:

Electrical Engineering; Engineering

Keywords:

Inverse Synthetic Aperture Radar, ISAR, Radar, Tomography, Tomographic Imaging, Radar Tomography, W-Band Radar Imaging, Millimeter Wave Radar Imaging, Distributed Aperture Array Radar

Rossler, Carl WAdaptive Radar with Application to Joint Communication and Synthetic Aperture Radar (CoSAR)
Doctor of Philosophy, The Ohio State University, 2013, Electrical and Computer Engineering
Until recently, the functionality of radar systems has been built into the radar's analog hardware, resulting in radars which are inflexible and that can only be used for a specific application. Modern systems, however, driven by the ever increasing speed of processors and data converters - analog-to-digital (ADC) and digital-to-analog (DAC) - are transitioning toward software defined radar (SDR) systems. The advent of SDRs inevitably leads to the question of how their added flexibilities can best be leveraged. The work within this dissertation is motivated by joint radar and communication functionality. The main objective is to study and demonstrate the ability of radar systems to employ non-traditional, specifically, communication waveforms for remote sensing. A software defined radar (SDR) is developed. The SDR features a "closed loop" testbed interface accessible via Matlab m-code. Here, "closed-loop" means that data can be pulled from the SDR, processed, then used to select/adapt the waveform and settings of the SDR without human intervention, i.e. on the fly. The testbed interface is used to implement a joint radar and communication system which is capable of collecting and processing radar data, e.g. range-Doppler maps, while simultaneously communicating previously collected radar data. Simultaneous functionality is accomplished by interrogating with a wide band digital communication waveform which is modulated with the previously collected radar data. The joint system is used to empirically demonstrate the theoretical work on detection and change detection within this dissertation. Optimal detectors are developed for interrogation with communication waveforms. The optimal detector for a single target with known impulse response in white noise is known to be a thresholding of the output of a matched filter. Radar systems, however, often operate in multi-target environments; notably air-to-ground synthetic aperture radars. For such applications, the hypothesis test which shows matched-filter/thresholding to be optimal does not well represent the conditions under which the radar is operating. The matched filter is, therefore, suboptimal due to substantial modeling error. The optimal detector is related to classical radar detectors. The expression for the performance of the optimal detector is given. Its performance is shown to be greater than or equal to that of the matched filter detector. Optimal coherent change detectors are developed for diverse waveform interrogation: i.e. when the reference and mission images are the result of interrogation with different waveforms. With waveform diversity, the problem of change detection becomes more challenging. The optimal coherent change detection (CCD) does not take the form of the classical CCD and is not prone to high false alarm rates in areas of low pixel intensity. Special cases of the optimal coherent change detector are given under which the change detector reduces to intuitively satisfying forms.

Committee:

Emre Ertin (Advisor); Randolph Moses (Advisor); Chris Baker (Committee Member)

Subjects:

Electrical Engineering

Keywords:

radar; software defined radar; SDR; waveform diversity; adaptive radar; synthetic aperture radar; SAR; detection; change detection; coherent change detection; CCD; communication; passive radar; noise radar

Abdelbagi, Hamdi EltayibFPGA-Based Coherent Doppler Processor for Marine Radar Applications
Doctor of Philosophy (Ph.D.), University of Dayton, 2016, Electrical Engineering
The goal of this research is to develop a method for affordable and reliable sampling and coherent processing of measurement data collected via a modified magnetron oscillator based marine radar system. Non-coherent low-priced marine radar systems offer limited surveillance in clutter rich environments as compared to more expensive and complex coherent solid state radar systems. The approach used herein leverages modern analog to digital converters (ADC) and field programmable gate array (FPGA) technology to affordably and effectively sample the radiated and received signals for further analysis using FFT-based Doppler processing or cross correlation analysis. Track processing of moving targets is fundamental to any advanced radar and is a further focus of this research. The marine radar hardware is modified to capture the transmit signal at the source, and the receive signal at the aperture, for processing via FPGAs. The receive pulse train is cross-correlated with the transmit pulse train reference to remove the uncertainties in the phase history of the collected data. This operation ultimately makes the radar fully coherent on receive. Once the receive signal is made coherent, classical Doppler processing is used to differentiate moving targets from clutter and electromagnetic interference. A real time system has been built on a board with ADCs, FPGAs, and a microprocessor. Mixing of the Transmit (TX) and the Receive (RX) signals, Fourier transform analysis, and Pulse Compression are all executed digitally in the FPGA whereas Doppler Processing is performed on the microprocessor. This paper presents the underlying principles of cohering signals on receive, and it will show a real-time implementation of such algorithms using FPGAs.

Committee:

Michael Wicks, PhD (Advisor); Lorenzo Lo Monte, PhD (Committee Chair); Guru Subramanyam, PhD (Committee Chair); Eric Balster, PhD (Committee Chair)

Subjects:

Electrical Engineering; Engineering

Keywords:

Radar; FPGA; FPGA Radar; Coherent Radar; non coherent radar; FPGA Doppler; FFT Doppler; Marine Radar; FPGA marine

Jones, Aaron M.Frequency Diverse Array Receiver Architectures
Master of Science in Engineering (MSEgr), Wright State University, 2011, Electrical Engineering

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 frequency matched. This practice neglects practical consideration in receiver implementation and has motivated research to formulate a design that includes all frequencies. We present several receiver architectures for a uniform linear FDA, and compare the processing chain and spatial patterns in order to formulate an argument for the most efficient design to maximize gain on target.

It may also be desirable to beamsteer in higher dimensionalities than a linear array affords, thus, the transmit and receive concept is extended to a generic planar array. This new architecture allows 3-D beamsteering in angle and range while maintaining practicality. The spatial patterns that arise are extremely unique and afford the radar designer an additional degree of freedom to develop operational strategy.

The ability to simultaneously acquire, track, image and protect assets is a requirement of future fielded systems. The FDA architecture intrinsically covers multiple diversity domains and, therefore, naturally lends it self to a multi-mission, multi-mode adar scheme. A multiple beam technique that uses coding is suggested to advance this notion.

Committee:

Brian Rigling, PhD (Advisor); Douglas Petkie, PhD (Committee Member); Fred Garber, PhD (Committee Member)

Subjects:

Electrical Engineering

Keywords:

radar; frequency diverse array radar; waveform diversity; antenna patterns; range-dependent beamforming; linear arrays; planar arrays; MIMO radar; frequency diversity; autonomous beam scanning; multiple beam radar

Chang, Paul ChinlingNear zone radar imaging and feature capture of building interiors
Master of Science, The Ohio State University, 2008, Electrical Engineering
Radar imaging techniques for building exteriors have been extensively studied over the past several years. However, through-wall imaging presents us with several challenges. Among them are (1) wall penetrating signal attenuation and distortion and (2) demand of adequate modeling techniques. This thesis begins by reviewing near zone imaging algorithms based on scattering centers, and proceeds with the adaptation of new heuristic edge and corner diffraction coefficients for dielectric wedges using transmission and reflection characteristics of multilayered slab to ensure shadow boundary continuity. The high frequency building characterizing technique is then validated against experimental radar measurement. By using the Ohio State University NEC-BSC code upgraded with the new diffraction coefficients, it is demonstrated that polarization and bistatic SAR can be used in detecting or avoiding certain building features and hidden objects. To improve interior wall and object imaging, the CLEAN algorithm is employed to remove exterior wall contributions using pre-computed scattering signatures.

Committee:

John Volakis (Advisor)

Keywords:

radar imaging; through-wall radar; building imaging; high frequency techniques; radar signature

Jones, Aaron M. Performance Prediction of Constrained Waveform Design for Adaptive Radar
Doctor of Philosophy (PhD), Wright State University, 2016, Engineering PhD
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 in selecting what to transmit. It is critical that the algorithms and performance prediction models developed be robust to varying radio frequency interference (RFI) environments. However, the current literature only provides toy examples not suitable in representing real-world interference. Therefore, we develop and validate two new power spectral density (PSD) models for interference and noise, derived from measured data, that allow us to ascertain the effectiveness of an algorithm under varying conditions. We then investigate the signal-to-interference-and-noise ratio (SINR) performance for a multi-constrained waveform design in the presence of colored interference. We set-up and numerically solve two optimization problems that maximize the SINR while applying a novel waveform design technique that requires the signal be an ordered subset of eigenvectors of the interference and noise covariance matrix. The significance of this work is the observation of the non-linearity in the SINR performance as a function of the constraints. This inspires the development of performance prediction models to obtain a greater understanding of the impact practical constraints have on the SINR. Building upon these results, we derive two new performance models, one for the constrained waveform SINR and one for the basis-dimension of the eigenvectors of the noise and interference covariance matrix required to achieve a particular modulus constraint. Radar waveforms typically require a constant modulus (constant amplitude) transmit signal to efficiently exploit the available transmit power. However, recent hardware advances and the capability for arbitrary (phase and amplitude) designed waveforms have forced a re-examination of this assumption to quantify the impact of modulus perturbation from phase only signals. The models are validated with measured data and through Monte Carlo (MC) simulation trials. Lastly, we develop the role of the integrated sidelobe (ISL) parameter for adaptive radar waveform design as it pertains to SINR performance. We seek to further extend the stateof- the-art by developing two new performance models for the integrated sidelobe metric. First, the corresponding SINR degradation, from optimal as the ISL constraint is applied and second, the basis dimension of the noise and interference covariance matrix required to generate the waveform. With our approach, we are able show exceptional ability to predict the impact to SINR as we tighten the ISL constraint in the waveform design. For all performance models, we include Monte Carlo simulation trials designed to measure the impact of ISL on SINR as well as compare performance when measured data is used to represent the interference and noise covariance matrix.

Committee:

Brian Rigling, Ph.D. (Advisor); Muralidhar Rangaswamy, Ph.D. (Committee Member); Christopher Baker, Ph.D. (Committee Member); Fred Garber, Ph.D. (Committee Member); Wu Zhiqiang, Ph.D. (Committee Member)

Subjects:

Aerospace Engineering; Electrical Engineering

Keywords:

radar;waveform design;signal processing;performance prediction;adaptive radar;cognitive radar;synthetic RFI;RFI

Almutiry, Muhannad Salem S.Extraction of Weak Target Features from Radar Tomographic Imagery
Doctor of Philosophy (Ph.D.), University of Dayton, 2016, Electrical Engineering
Radio Frequency (RF) Tomography is a mathematical process of 3D image reconstruction from a measurement using a multistatic distribution of transmitters and receivers. The geometric diversity of these elements increases the information in the measurements. The process of determining the permittivity and conductivity profile in the measurement domain, and, therefore, the shape of the target, from the scattered field measurements, is an inverse problem. To solve this problem, under conventional methods such as the Born approximation, we use the principles of linear scattering to determine a linear relationship between measured returns and target shape. The Born approximation is valid if the scatterer is small and does not interact strongly with other objects. However, strong scatterers within the domain may generate sidelobes masking weaker returns. This masking, in conjunction with multipath effects, may result in loss of features and subsequent failure to identify a target. In this research, a novel method is proposed to increase overall image quality and extend the capabilities of RF tomography by modeling the strong scatterers in the measurement domain as dipoles that behave as secondary sources (transmitters). Unlike conventional methods, the dipole model reduces the effects of the sidelobes from the strong scatterers and exploits the multipath of multiple targets or complex shapes. The multipath phenomena contains more information about the targets permitting illumination in the shadowed region and an increase to the radar aperture length. The electromagnetic characteristics for each modeled dipole are estimated by representing the cells in the measurement domain's image. The eigenvalue and eigenvector from each cell represent the phase and magnitude for the modeled dipole and also the spatial orientation of the target. The process of modeling large scatterers as dipoles can be iterated, addressing one strong scatterer at a time. This method effectively suppresses the sidelobes and exploits the multipath within the measurement domain. Using the Born approximation, the linear relationship between the scattered fields and the target is updated for simplicity. With iterations, the “extra” dipole will account for the multipath effects, thus removing some limitations caused by the Born approximation. This concept has been successfully demonstrated in software (FEKO© by Altair). In addition, this work also presents an innovative conversion using a back-projection algorithm for multipath effects and modeling of an “additional” source or transmitter in the measurement domain. The result of implementing this method of modeling strong scatterers as dipoles successfully demonstrated an increase in the resolution and enhanced radar imagery.

Committee:

Michael Wicks (Advisor); Keigo Hirakawa (Committee Member); John Loomis (Committee Member); Lorenzo Lo Monte (Committee Member)

Subjects:

Electrical Engineering

Keywords:

Born Approximation; Radar imaging; synthetic aperture radar; Microwave imaging; ground penetrating radar; Radio frequency tomography

Simms, Melissa JeanA Novel Approach to Target Scene Detection and Identification: Theory & Experiments
Master of Science, Miami University, 2016, Computational Science and Engineering
This thesis presents theoretical analysis and experimental evidence to demonstrate the feasibility of an ultra-wideband (UWB) software-de fined radar sensor (SDRS) for detection and identifi cation of targets in a three-dimensional target scene. Orthogonal frequency division multiplexing (OFDM) is used to modulate the UWB SDRS signal. Spectral responses from targets at each of the OFDM sub-carriers are investigated experimentally and the results are used to develop frequency pro lfies as the viewing angle of the SDRS changes with respect to the target. These pro files are then used to perform detection and identi fication of targets when characteristics of those targets are known. Simulations and experiments are presented to illustrate the eff ectiveness of the detection and identi fication algorithms which are the primary focus of this thesis.

Committee:

Dmitriy Garmatyuk, Dr. (Advisor); Chi-Hao Cheng, Dr. (Committee Member); Mark Scott, Dr. (Committee Member)

Subjects:

Electrical Engineering

Keywords:

radar target identification; OFDM; UWB radar; GLRT; radar sensing; frequency-angle profile analysis

Callahan, Michael J.Estimating Channel Identification Quality in Passive Radar Using LMS Algorithms
Doctor of Philosophy (PhD), Wright State University, 2017, Engineering PhD
Passive bistatic radar can be an attractive choice relative to monostatic radar because it provides the ability to operate covertly; immunity to jamming and interference; the ability to operate outside of traditional radar bands; and reduced cost. The benefits of noise waveforms versus classic radar waveforms such as linear frequency modulation (LFM) are discussed in the literature. Noise waveforms, with their thumbtack ambiguity functions, are ideal for use in non-cooperative passive radar. Since many digital waveforms are randomized to make their spectra approximately white, noise-like waveforms may be readily available for opportunistic use by non-cooperative passive radar receivers. For instance, the literature points out that digital television transmitters offer a powerful, well-defined signal with sufficient bandwidth for reasonable precision in range and are noise-like, thereby allowing for good, consistent range compression and Doppler estimation of targets. Much of the literature assumes that the transmitted noise (or noise-like) waveform is white (flat spectrum) over a finite bandwidth, and with good reason. However, some illuminators may emit waveforms that are not white. When the transmitted waveform’s spectrum is colored (correlated), the cross-correlation process is likely to produce unacceptably high sidelobes. Meanwhile, LMS may produce more acceptable sidelobes. Until now, no theoretical expressions for the SNR at the output of the LMS family of algorithms existed in the literature for cases in which variants of the LMS algorithm are used to process colored Gaussian noise input data. The original contribution of this research is as follows. An equation is derived which predicts the theoretical output SNR when processing colored Gaussian noise input data using conventional LMS, valid at steady-state. Theoretical results have been corroborated by simulation results, and this contribution has been completed. The equation which predicts the steady-state theoretical output SNR when conventional LMS processes colored Gaussian noise input data should also apply at steady-state when block LMS and fast block LMS (fast LMS) are used to perform the processing. Additionally, promising simulation results using L1 LMS are presented, which highlight the previously known fact that L1 LMS’s performance when processing sparse input data may be robust even when the transmit waveform’s spectrum is notched, while results from other algorithms (including conventional LMS) noticeably degrade. These simulation results prompt future research to extend the contribution documented herein by deriving the steady-state theoretical output SNR when processing sparse colored Gaussian noise input data using L1 LMS.

Committee:

Brian Rigling, Ph.D. (Committee Chair); Fred Garber, Ph.D. (Committee Member); Arnab Shaw, Ph.D. (Committee Member); Michael Temple, Ph.D. (Committee Member); Muralidhar Rangaswamy, Ph.D. (Committee Member)

Subjects:

Electrical Engineering

Keywords:

channel identification; passive radar; noise radar; noise-like radar; least mean square; LMS

Komarabathuni, Ravi V.Performance Assessment of a 77 GHz Automotive Radar for Various Obstacle Avoidance Application
Master of Science (MS), Ohio University, 2011, Electrical Engineering (Engineering and Technology)

Human safety is one of the highest priorities in the automotive industry. The demands made for reliable safety systems have been increasing tremendously in the past decade. The radar sensors used for safety systems should be capable of detecting not only automobiles but also motorcycles, bicycles, pedestrians, roadside objects and any other obstacles the vehicle may come in contact with.

This thesis investigates several performance aspects and test procedures for a 77 GHz long range radar sensor with different test target objects. This assessment helps to investigate the potential to use these radar sensors for obstacle detection and/or avoidance for smaller objects like bicycles, humans, traffic barrels, 4” poles, metal sheets, and also for bigger objects like vans, motorcycles, aircraft, etc. For these purposes, different test cases were developed to evaluate the performance. The different test cases used to test a 77 GHz radar sensor includes: finding maximum range, range accuracy, finding maximum field of view, detection (& separation) of two target objects (similar & different) at different radial distances, and maximum range for detecting an aircraft. Observations were made with the radar sensor mounted on a moving cart and the measurements were logged. The results from these tests will provide insight into analyzing the possibilities and limitations of these radar sensors for different applications.

The tests were successfully conducted on a flat, open field at Ohio University Airport, Albany, OH.

Committee:

Chris Bartone, PhD, P.E. (Advisor); Jeffrey Dill, PhD (Committee Member); Bryan Riley, PhD, PMP (Committee Member); William Kaufman, PhD (Committee Member)

Subjects:

Automotive Engineering; Electrical Engineering

Keywords:

Long Range Radar (LRR); Adaptive Cruise Control (ACC); 77 GHz Radar Sensor; Obstacle Detection and/or Avoidance Application;Target Object Detection by Radar Sensor; Safety in Automotive Industry

Kizhakkel, Vinit RajanPULSED RADAR TARGET RECOGNITION BASED ON MICRO-DOPPLER SIGNATURES USING WAVELET ANALYSIS
Master of Science, The Ohio State University, 2013, Electrical and Computer Engineering
Radar based automatic target recognition systems are commonly used in perimeter protection and surveillance applications. These systems determine the nature of a target moving in the radar's field of view using its echo signal. Such an echo signal contains the target's micro-Doppler (μ-D) signature as well as its macro-motion related parameters. This thesis presents and compares three different approaches to develop such a system to distinguish between humans, dogs and background clutter using a low power pulsed radar. Each of these approaches rely on one among three different joint time-frequency transforms such as the short-time Fourier transform, the wavelet packet transform and the Haar transform to extract key μ-D signature related features from the time-frequency plane representation of the echo signal. These μ-D signature based features are combined with relative range profile based ones that characterize the detected target's motion at a gross level. These features, extracted from a variety of field data, are used to train and test different classifiers that finally declare the type of the target. The comparative performances of these three methods have been discussed. The Haar transform based approach, in particular, seems to show promise for implementation on computationally constrained platforms like motes used in wireless sensor network applications.

Committee:

Ashok Krishnamurthy, PhD (Advisor); Rajiv Ramnath, PhD (Committee Member)

Subjects:

Computer Science; Electrical Engineering; Engineering

Keywords:

radar; pulsed radar; target recognition; wavelet; micro-Doppler

Moore, Linda JenniferImpact of Phase Information on Radar Automatic Target Recognition
Doctor of Philosophy (Ph.D.), University of Dayton, 2016, Electrical Engineering
Traditional synthetic aperture radar (SAR) systems tend to discard phase information of formed complex radar imagery prior to automatic target recognition (ATR). This practice has historically been driven by available hardware storage, processing capabilities, and data link capacity. Recent advances in high performance computing (HPC) have enabled extremely dense storage and processing solutions. Therefore, previous motives for discarding radar phase information in ATR applications have been mitigated. First, we characterize the value of phase in one-dimensional (1-D) radar range profiles and two dimensional (2-D) SAR imagery with respect to the ability to correctly estimate target features, which are currently employed in ATR algorithms for target discrimination. These features correspond to physical characteristics of a target through radio frequency (RF) scattering phenomenology. Physics-based electromagnetic scattering models developed from the geometrical theory of diffraction are utilized for the information analysis presented here. Information is quantified by the error of target parameter estimates from noisy radar signals when phase is either retained or discarded. Operating conditions (OCs) of signal-to-noise ratio, bandwidth, and aperture extent are considered. Second, we investigate the value of phase in 1-D radar returns with respect to the ability to correctly classify canonical targets. Classification performance is evaluated via three techniques, namely, naïve Bayes, logistic regression and a bound on Bayes error rate (BER). These classification techniques maintain varying assumptions on the observed data set, with the BER bound making no assumptions. In each case, phase information is demonstrated to improve radar target classification rates.

Committee:

Robert Penno (Committee Chair); Brian Rigling (Advisor)

Subjects:

Electrical Engineering

Keywords:

synthetic aperture radar; high range resolution; radar range profiles; phase information; target feature estimation; position accuracy; error variance; Cramer-Rao lower bound; operating conditions; automatic target recognition

Chang, Paul ChinlingPhysics-Based Inverse Processing and Multi-path Exploitation for Through-Wall Radar Imaging
Doctor of Philosophy, The Ohio State University, 2011, Electrical and Computer Engineering

Microwave imaging of hidden targets in a complex scattering medium has drawn much attention as it can be used to gather information of concealed targets. Among these, through-wall radar imaging (TWI) is an emerging technology for “seeing” through walls to determine building layout and occupancy. This dissertation focuses on the development of special signal processing techniques to address the impact of wall distortion on the interior image. The goal is to develop radar imaging techniques that incorporate electromagnetic propagation models of the wall structure to improve target restoration.

This dissertation begins by establishing an understanding of the fundamental synthetic aperture radar (SAR) imaging principles along with its model-based extension to mitigate the wall reflection and propagation delays of the uniform dielectric walls (multiple layers). Specifically, wall compensation is carried out via an Adaptive CLEAN (A-CLEAN) and target refocusing algorithm. Subsequently, periodic wall structures are characterized using Floquet modal analysis and plane wave spectral expansion (PWE). To further improve the computational efficiency, a high-frequency ray model that approximates the exact solution by a set of rays is also presented. It is shown that the structural periodicity induces higher-order space harmonics leading to risen clutter and ghost artifacts in the through-wall image.

To overcome these distortions, this dissertation presents a model-corrected inverse imaging framework that incorporates the periodic layer Green’s function into its forward model. For that, a linear back-projection solution and a nonlinear minimization solution are applied to solve the inverse problem. The back-projection image corrects the distortion and has higher resolution compared with free space due to inclusion of multi-path propagation through the periodic wall, but considerable sidelobe clutter is also present. On the other hand, the nonlinear solution not only corrects target distortion without clutter, but also reduces the solution to a sparse form.

A multi-path imaging approach is also proposed to exploit the multi-scattering effects more directly to our advantage. Specifically, the imaging kernel of the back-projection method is designed to focus any propagation paths of interest. Subsequently, an adaptive sidelobe reduction technique based on spatially-variant apodization (SVA) is applied to suppress the unwanted sidelobes. It is shown that the Floquet modes of the periodic structure greatly increase the effective radar aperture leading to much improved target resolution than that in free space. The research findings can also be attractive to other microwave imaging applications.

Committee:

Robert Burkholder, PhD (Advisor); John Volakis, PhD (Advisor); Fernando Teixeira, PhD (Committee Member)

Subjects:

Electrical Engineering; Electromagnetics

Keywords:

Through-wall radar imaging; radar signal processing, image retoration, super-resolution technique, sparse imaging, multi-path exploitation, electromagnetic modeling

Fogle, Orelle RyanHuman Micro-Range/Micro-Doppler Signature Extraction, Association, and Statistical Characterization for High-Resolution Radar
Doctor of Philosophy (PhD), Wright State University, 2011, Engineering PhD
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 µR data. We apply this algorithm to measured data to gain knowledge of dismount-radar phenomenology. Specifically, we associate µD/µR features to physical human components resulting in an intuitive and physically-relevant model. Additionally, we statistically characterize the radar cross-section (RCS) behavior of the individual body features.

Committee:

Brian Rigling, PhD (Advisor); Lee Potter, PhD (Committee Member); Fred Garber, PhD (Committee Member); Ronald Riechers, PhD (Committee Member); Michael Raymer, PhD (Committee Member)

Subjects:

Electrical Engineering; Remote Sensing

Keywords:

radar; dismount; micro-Doppler; micro-range; radar cross-section

Lopez-Castellanos, VictorUltrawideband Time Domain Radar for Time Reversal Applications
Doctor of Philosophy, The Ohio State University, 2011, Electrical and Computer Engineering

An ultrawide band (UWB) time domain (TD) radar has been developed for Time Reversal (TR) synthetic inverse scattering. This work describes the fabrication and test of a time domain TR “mirror” (TRM), which is the system that transmits, receives, and processes TR signals. Time reversal electromagnetics is a family of signal processing techniques that exploit the time reversal invariance of Maxwell equations, and allow focusing of waves in space and time with “super resolution”, i.e. beyond the classical resolution limit. In a typical TR experiment, first a pulsed signal is emitted and scattered by a target, which then acts as a weak emitter “source” toward the TRM. Then the TRM senses and records the weak scattered signal. Next, the recorded signals are time-reversed for their subsequent normalization and reradiation into the medium. The result is a signal that focuses in time and space where the target originally was, permitting localization and identification applications.

A 12 mW low power short range experimental verification of the above process in the microwave domain is demonstrated in this work. The developed system exhibits a 40 GHz useful bandwidth such as to be able to follow 12 ps transition duration signals without distortion. An antenna system was designed and fabricated to satisfy the above bandwidth specification. The backward propagation in the TR process is executed synthetically on account of the current state of the required technology to recreate ultra-fast signals of arbitrary shape.

Owing to its intrinsic TD nature, the finite difference time-domain (FDTD) method was applied as the numerical engine to simulate the electromagnetic fields in the TR process, facilitating the link between acquired data and its interpretation. The system designed showed capable of recreating in TD, with this extended bandwidth, the standard TR experiment as predicted by the theory. Hence, from real measurements the system was able to recreate synthetically space and time focusing. This kind of system could have application in subsurface target detection, trough-wall imaging and novel wireless communications.

Additionally, in this work a numerical study introducing a novel technique to estimate the (mean) effective permittivity of a random media applying TR techniques is presented, and for which high performance computing was required to process the data. The results showed that TR can be applied to determine effective permittivity of random media difficult to otherwise model deterministically.

Committee:

Fernando Teixeira, Dr. (Advisor); Roberto Rojas, Dr. (Advisor); Patrick Roblin, Dr. (Committee Member)

Subjects:

Electrical Engineering; Electromagnetics; Electromagnetism

Keywords:

time reversal; tr; inverse scattering; uwb; radar; time domain; random media; random medium; conical antenna; TEM horn;tr mirror; time reversal mirror; deconvolution; DORT; impulse radar;

Burwell, AlexExperimental Testing and Evaluation of Orthogonal Waveforms for MIMO Radar with an Emphasis on Modified Golay Codes
Master of Science (M.S.), University of Dayton, 2014, Electrical Engineering
Coherent Multiple Input Multiple Output (MIMO) Radar utilizes orthogonal waveforms to allow for formation of both transmit and receive beams on receive. Many waveform sets have been proposed to accomplish this task: Orthogonal Frequency Division Multiplexing (OFDM), Linear Frequency Modulation on the Pulse (LFMOP), Noise waveforms, Golay Codes, Deng Codes etc. In "A novel polyphase code for sidelobe suppression,” Searle et al. proposed a special set of Modified Golay Codes that take advantage of a polyphase modulator along with frequency diversity to achieve orthogonality; however, this type of code increases the required number of sensor outputs along with the total bandwidth of the system to achieve its results. It is much more convenient to operate a MIMO system over a single bandwidth of interest while achieving sufficient orthogonality for Virtual Beamforming (VBF). This paper presents the experimental results for the simulation, in-the-loop testing, and open-air experimentation of the Modified Golay Code, LFMOP, and the windowed LFMOP. By testing the orthogonality of the modulation schemes while operating over the same bandwidth in a real environment, the research provides valuable feedback to guide future MIMO experimentation.

Committee:

Michael Wicks, Dr. (Advisor); Lorenzo Lo Monte, Dr. (Committee Member); Guru Subramanyam, Dr. (Committee Member)

Subjects:

Electrical Engineering

Keywords:

MIMO Radar; Multiple Input Multiple Output Radar; Golay codes; Golay sequences; Golay Complementary seqeunces

Wang, HuaiyiAchieving Efficient Spectrum Usage in Passive and Active Sensing
Doctor of Philosophy, The Ohio State University, 2017, Electrical and Computer Engineering
Increasing demand for supporting more wireless services with higher performance and reliability within the frequency bands that are most conducive to operating cost-eff ective cellular and mobile broadband is aggravating current electromagnetic spectrum congestion. This situation motivates technology and management innovation to increase the efficiency of spectral use. If primary-secondary spectrum sharing can be shown possible without compromising (or while even improving) performance in an existing application, opportunities for efficiency may be realizable by making the freed spectrum available for commercial use. While both active and passive sensing systems are vitally important for many public good applications, opportunities for increasing the efficiency of spectrum use can be shown to exist for both systems. This dissertation explores methods and technologies for remote sensing systems that enhance spectral efficiency and enable dynamic spectrum access both within and outside traditionally allocated bands.

Committee:

Joel Johnson (Advisor); Emre Ertin (Committee Member); Graeme Smith (Committee Member)

Subjects:

Electrical Engineering; Electromagnetics

Keywords:

spectrum sharing; air traffic control radar; LTE system; passive radar; microwave radiometry

Fofie, Francis ObengModel prediction of the effects of ameliorating cosmetics on the performance of airport surveillance radar and air traffic control radar beacon systems
Master of Science (MS), Ohio University, 2003, Electrical Engineering & Computer Science (Engineering and Technology)
Model prediction of the effects of ameliorating cosmetics on the performance of airport surveillance radar and air traffic control radar beacon systems.

Committee:

Simbo Odunaiya (Advisor)

Keywords:

Prediction Model; Ameliorating Cosmetics; Airport Surveillance Radar; Traffic Control Radar; Beacon Systems

Butterfield, Aaron SUsing Synthetic Cognits and The Combined Cumulative Squared Deviation as Tools to Quantify the Performance of Cognitive Radar Algorithms
Master of Science, The Ohio State University, 2016, Electrical and Computer Engineering
The computational speed of computing has pushed the digital arm of the radar closer to the antenna, allowing for more flexibility in radar platforms. In conjunction, human cognition has been an interesting case study for building cognitive algorithms for radar platforms. These algorithms employ a perception-action cycle as the base of their functionality. Scaling cognitive algorithms to show high level cognition has been relatively little progress because of the complexity in visualizing the scope of cognitive algorithms. In addition, there has been little forward motion on how to analyze the performance of cognitive algorithms. As a result, this thesis introduces the concept of a synthetic cognit as an abstraction to defining cognition in a radar platform. It introduces the loop diagram as a way to specify the scope of a synthetic cognit that allows an engineer to quickly see the hierarchical connection between a particular synthetic cognit and any other. Once the cognit is defined, goals are established as a control interface to the synthetic cognit. The performance of the algorithm is then calculated using a Combined Cumulative Squared Deviation (CCSD) and Cumulative Coherent Processing Interval (CCPI). This is done by comparing the CCSD and CCPI of the cognit with certain Static Radar Equivalents (SREs) and with other synthetic cognits. It is found that the CCSD and CCPI are effective metrics for quantifying the performance of cognitive algorithms but are highly dependent on the environment to truly compare performance.

Committee:

Graeme Smith, Ph.D (Advisor); Fernando Teixeira, Ph.D (Committee Member)

Subjects:

Electrical Engineering

Keywords:

cognitive radar, cognit, radar, quantification, cognitive algorithm, Fuster, Haykin

Ghosh, AmritaOptimum Waveform Scheduling with Software Defined Radar for Tracking Applications
Master of Science, The Ohio State University, 2010, Electrical and Computer Engineering

There has been tremendous advancement of digital technology over the past years. With the availability of high speed analog to digital (A/D) and digital to analog (D/A) converters, digital signal processor (DSP) enabled real-time processors with fast field programmable gate arrays (FPGAs), it is now possible to build a software defined radar (SDR), which is capable of switching transmit-waveforms adaptively on-the-fly at each pulse repetition interval (PRI). Using SDR it is possible to improve resolution by transmitting waveforms which are adapted to the scene. It is also possible to perform multi-mode operation such as combination of tracking and imaging. To exploit SDR's huge capability in terms of adaptive waveform selection in an efficient way, it is now necessary to study different waveforms and build optimum waveform scheduling techniques for different radar operations.

In this thesis we consider the problem of waveform scheduling for multiple range-Doppler radars operating collaboratively for target tracking. First, we consider the canonical case of collocated radar platforms, each capable of choosing a waveform at every PRI from a fixed chirp waveform library. We assume the radars fuse the information that they obtain from their measurements after each chirp pulse in a Kalman Filter tracking framework to obtain the posterior distribution of the target state. The radars then use the resulting distribution to jointly select their next waveform set. Our results extend previous work on information theoretic waveform-scheduling proposed for single range-Doppler radar to multiple radars interrogating the same target. We show that the radar platforms must employ a mixture of minimum and maximum chirp-rates supported by the radar hardware to maximize mutual information between the target state and measurements. Finally, the results are extended to an arbitrary number of radars located at arbitrary positions in 2-D plane. Thus, we show that to achieve improved radar tracking performance with multiple range-Doppler radars, out of infinite possibilities of chirp waveforms, the optimum waveform library needs to contain only two chirp waveforms with the minimum and maximum allowable chirp rates.

Committee:

Emre Ertin, PhD (Advisor); Lee Potter, PhD (Advisor)

Subjects:

Electrical Engineering

Keywords:

Waveform scheduling; Software defined radar; Radar; Tracking

Chen, MingCharacterization of Pedestrian Electromagnetic Scattering at 76-77GHz
Doctor of Philosophy, The Ohio State University, 2013, Electrical and Computer Engineering
Automobile safety system has received tremendous attention in the past few years. Radar used in such system must be capable of detecting not only other vehicles but also pedestrian. Automobile radar working at 24GHz has been used in blind-spot detection (BSD) and automatic cruise control (ACC) system to track the distance and relative speed of on-road object. However, existing radars are limited to short detection range (30m) and low spatial resolution, making them less useful for pedestrian detection. A new frequency band 76-77GHz, recently designated by the Federal Communication Commission (FCC), the International Telecommunication Union (ITU) in Europe, and the Ministry of Internal Affairs and Communications (MIC) in Japan for vehicular radar. At such high frequencies, a longer detection range (100m-150m) and better resolution can be achieved. As such, it will enable more reliable detection of pedestrians in front of vehicles with lower false alarm rate. In on-road environment, multiple radar reflections may be generated from clutters like trees, trash cans, road surface, curbs and other vehicles. Therefore, it is necessary to identify unique pedestrian radar signatures in the 76-77GHz band to help discriminate them from clutters. Experimental characterization of radar response of human targets at such high frequencies is not trivial and often inaccurate due to extremely short wavelength which makes radar measurement very sensitive to uncertainties associated with body position, orientation, and breathing motion. The variations produced by these uncertainties severely affect the reliability of the radar features extracted from measurement. In addition, the almost infinite combination of clothes, accessories and body postures significantly increase the time and resource required by this approach. In this dissertation, analysing pedestrian radar signatures in the 76-77GHz band via numerical simulations is proposed to overcome the issues with measurements. Without the impact of human body motion and posture uncertainties, it should be more reliable and cost effective to study pedestrian scattering signature via numerical model simulations. The trade-off between simulation accuracy and computation efficiency was studied for different mesh sizes. Simplified human model using maximal acceptable mesh size was adopted to substantially reduce the computer memory and simulation time while maintaining desired accuracy. Utilizing optimized numerical simulation setup, pedestrian radar signatures study were carried out for human with different body features and in different postures. Several significant radar features as well as the corresponding feature extraction methods were proposed and studied. Measured radar response of human subjects using a custom designed 76-78GHz up/down converter module was employed to validate the radar signatures from numerical simulations. Measurement system requirement to obtain reliable data was analysed. Clutter removal processing was introduced to remove the undesired environment impact on the human RCS response. Good agreement between simulations and measurements confirmed the effectiveness and reliability of the radar features extracted from simulation. Based on radar response study of human subjects, a radar mannequin was designed by the Ohio State University (OSU) and Indiana University-Purdue University Indianapolis (IUPUI) to reproduce radar response of human at all observation angle. The mannequin can then be used to evaluate the effectiveness of a radar based active safety system mounted on vehicle. As part of this effort, a novel multi-layered artificial skin design was proposed and demonstrated to have similar reflectivity to the actual human skin. This artificial skin was adopted to cover the mannequin. Measured RCS patterns of mannequin showed similar radar features to human subjects of similar shapes.

Committee:

Chi-Chih Chen (Advisor); John Volakis (Advisor); Baker Christopher (Committee Member); Olli Tuovinen (Committee Member)

Subjects:

Electrical Engineering; Electromagnetism

Keywords:

Radar measurements, radar cross-sections, remote sensing, active safety

Stewart, Kyle BradleyWaveform-Diverse Multiple-Input Multiple-Output Radar Imaging Measurements
Doctor of Philosophy, The Ohio State University, 2016, Electrical and Computer Engineering
Multiple-input multiple-output (MIMO) radar is an emerging set of technologies designed to extend the capabilities of multi-channel radar systems. While conventional radar architectures emphasize the use of antenna array beamforming to maximize real-time power on target, MIMO radar systems instead attempt to preserve some degree of independence between their received signals and to exploit this expanded matrix of target measurements in the signal-processing domain. Specifically the use of sparse “virtual” antenna arrays may allow MIMO radars to achieve gains over traditional multi-channel systems by post-processing diverse received signals to implement both transmit and receive beamforming at all points of interest within a given scene. MIMO architectures have been widely examined for use in radar target detection, but these systems may yet be ideally suited to real and synthetic aperture radar imaging applications where their proposed benefits include improved resolutions, expanded area coverage, novel modes of operation, and a reduction in hardware size, weight, and cost. While MIMO radar's theoretical benefits have been well established in the literature, its practical limitations have not received great attention thus far. The effective use of MIMO radar techniques requires a diversity of signals, and to date almost all MIMO system demonstrations have made use of time-staggered transmission to satisfy this requirement. Doing so is reliable but can be prohibitively slow. Waveform-diverse systems have been proposed as an alternative in which multiple, independent waveforms are broadcast simultaneously over a common bandwidth and separated on receive using signal processing. Operating in this way is much faster than its time-diverse equivalent, but finding a set of suitable waveforms for this technique has proven to be a difficult problem. In light of this, many have questioned the practicality of MIMO radar imaging and whether or not its theoretical benefits may be extended to real systems. Work in this writing focuses specifically on the practical aspects of MIMO radar imaging systems and provides performance data sourced from experimental measurements made using a four-channel software-defined MIMO radar platform. Demonstrations of waveform-diverse imaging data products are provided and compared directly against time-diverse equivalents in order to assess the performance of prospective MIMO waveforms. These are sourced from the pseudo-noise, short-term shift orthogonal, and orthogonal frequency multiplexing signal families while experimental results demonstrate waveform-diverse measurements of polarimetric radar cross section, top-down stationary target images, and finally volumetric MIMO synthetic aperture radar imagery. The data presented represents some of the first available concerning the overall practicality of waveform-diverse MIMO radar architectures, and results suggest that such configurations may achieve a reasonable degree of performance even in the presence of significant practical limitations.

Committee:

Joel Johnson (Advisor); Robert Burkholder (Committee Member); Emre Ertin (Committee Member)

Subjects:

Electrical Engineering; Remote Sensing

Keywords:

MIMO radar; MIMO SAR; radar imaging; virtual array; waveform-diversity;

Gorham, LeRoy A.Large Scene SAR Image Formation
Doctor of Philosophy (PhD), Wright State University, 2015, Engineering PhD
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 expressions for PFA phase errors to accurately determine scene size limitations, with examples provided for linear and circular flight paths. Third, we develop a novel adaptation of PFA which corrects a significant amount of the phase errors, thereby greatly increasing the allowable scene size of the algorithm. These results are demonstrated using both simulated and measured SAR data sets.

Committee:

Brian Rigling, Ph.D. (Advisor); Fred Garber, Ph.D. (Committee Member); John Emmert, Ph.D. (Committee Member); Michael Bryant, Ph.D. (Committee Member); Randolph Moses, Ph.D. (Committee Member)

Subjects:

Electrical Engineering

Keywords:

radar; synthetic aperture radar; polar format algorithm; phase error analysis

Christman, Jordan LouisEfficient Digital Spotlighting Phase History Re-Centering Hardware Implementation
Master of Science (M.S.), University of Dayton, 2016, Electrical Engineering
This thesis focuses on the study of the SAR algorithm digital spotlighting and the hardware implementation of the phase history re-centering portion of the algorithm. The phase history re-centering portion of the digital spotlighting algorithm re-centers the phase history data with respect to the new scene center. This thesis provides a solution that allows for a single precision implementation of the phase history re-centering in hardware that provides comparable results to that of a double precision implementation. In order to attain a higher order of precision the frequency sample values were scaled. Scaling the frequency samples allows the use of single precision floating point data types while maintaining on average 8 decimal places of precision when compared to a double precision floating point data type implementation. By using single precision floating point data types a resource reduction of 46% can be achieved when compared to a double precision floating point data types. The hardware implementation of the phase history re-centering core provides a possible 36X speed up when compared to the MATLAB implementation. Leveraging this design would be a major step towards implementing the entire digital spotlighting algorithm on a low SWAP(Size Weight and Power) system. This low SWAP system may include platforms such as UAV's or any other SWAP constrained system.

Committee:

Eric Balster (Advisor)

Subjects:

Electrical Engineering; Engineering

Keywords:

Synthetic Aperture Radar; Digital Spotlighting; DSP Builder; Radar Signal Processing

Bryant, Christine AnnMultiple-Input Single-Output Synthetic Aperture Radar and Space-Time Adaptive Processing
Master of Science, The Ohio State University, 2010, Electrical and Computer Engineering
This thesis investigates the plausibility of implementing a multiple-input single-output (MISO) synthetic aperture radar (SAR) system for space-time adaptive processing (STAP) with a limited data rate requirement of a single receiver. A MISO-SAR system could provide processing flexibility to radar systems such as the Gotcha radar system developed at the Air Force Research Laboratory. Gotcha is an airborne wide-beam multi-mode radar system used to cover a large area for surveillance. In order to apply multiple algorithms to a large amount of data in real time, the data is downlinked to a supercomputer on the ground. STAP is an adaptive filtering technique, which can be used for improved detection of slow moving targets in the presence of clutter. However, STAP is typically implemented using an array of receiving elements, which significantly increases the data rate for downlinking to the ground. While MISO systems are common in communications applications, it is not a common radar system design approach. The MISO system requires additional waveform design considerations in order to obtain orthogonal transmit waveforms. However, the MISO system provides the additional degrees of freedom needed to apply STAP while maintaining a single receiver data rate.

Committee:

Lee Potter, PhD (Advisor); Emre Ertin, PhD (Committee Member)

Subjects:

Electrical Engineering

Keywords:

radar; signal processing; SAR; MISO radar; STAP; space-time adaptive processing

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