MIMO Radar Waveform Design and Sparse Reconstruction for Extended Target Detection in Clutter

This dissertation explores the detection and false alarm rate performance of a novel transmit-waveform and receiver filter design algorithm as part of a larger Compressed Sensing (CS) based Multiple Input Multiple Output (MIMO) bistatic radar system amidst clutter. Transmit-waveforms and receiver filters were jointly designed using an algorithm that minimizes the mutual coherence of the combined transmit-waveform, target frequency response, and receiver filter matrix product as a design criterion. This work considered the Probability of Detection (P D) and Probability of False Alarm (P FA) curves relative to a detection threshold, τ th, Receiver Operating Characteristic (ROC), reconstruction error and mutual coherence measures for performance characterization of the design algorithm to detect both known and fluctuating targets and amidst realistic clutter and noise. Furthermore, this work paired the joint waveform-receiver filter design algorithm with multiple sparse reconstruction algorithms, including: Regularized Orthogonal Matching Pursuit (ROMP), Compressive Sampling Matching Pursuit (CoSaMP) and Complex Approximate Message Passing (CAMP) algorithms. It was found that the transmit-waveform and receiver filter design algorithm significantly outperforms statically designed, benchmark waveforms for the detection of both known and fluctuating extended targets across all tested sparse reconstruction algorithms. In particular, CoSaMP was specified to minimize the maximum allowable P FA of the CS radar system as compared to the baseline ROMP sparse reconstruction algorithm of previous work. However, while the designed waveforms do provide performance gains and CoSaMP affords a reduced peak false alarm rate as compared to the previous work, fluctuating target impulse responses and clutter severely hampered CS radar performance when either of these sparse reconstruction techniques were implemented. To improve detection rate and, by extension, ROC performance of the CS radar system under non-ideal conditions, this work implemented the CAMP sparse reconstruction algorithm in the CS radar system. It was found that detection rates vastly improve with the implementation of CAMP, especially in the case of fluctuating target impulse responses amidst clutter or at low receive signal to noise ratios (β n). Furthermore, where previous work considered a τ th=0, the implementation of a variable τ th in this work offered novel trade off between P D and P FA in radar design to the CS radar system. In the simulated radar scene it was found that τ th could be moderately increased retaining the same or similar P D while drastically improving P FA. This suggests that the selection and specification of the sparse reconstruction algorithm and corresponding τ th for this radar system is not trivial. Rather, a tradeoff was noted between P D and P FA based on the choice and parameters of the sparse reconstruction technique and detection threshold, highlighting an engineering trade-space in CS radar system design. Thus, in CS radar system design, the radar designer must carefully choose and specify the sparse reconstruction technique and appropriate detection threshold in addition to transmit-waveforms, receiver filters and building the dictionary of target impulse responses for detection in the radar scene

Aircraft Safety and Operating Problems

Results of NASA research in the field of aircraft safety and operating problems are discussed. Topics include: (1) terminal area operations, (2) flight dynamics and control; (3) ground operations; (4) atmospheric environment; (5) structures and materials; (6) powerplants; (7) noise; and (8) human factors engineering

The 1991 International Aerospace and Ground Conference on Lightning and Static Electricity, volume 2

The proceedings of the conference are reported. The conference focussed on lightning protection, detection, and forecasting. The conference was divided into 26 sessions based on research in lightning, static electricity, modeling, and mapping. These sessions spanned the spectrum from basic science to engineering, concentrating on lightning prediction and detection and on safety for ground facilities, aircraft, and aerospace vehicles

NBS monograph

From Abstract: "This is a tutorial Monograph describing various aspects of time and frequency (T/F). Included are chapters relating to elemental concepts of precise time and frequency; basic principles of quartz oscillators and atomic frequency standards; historical review, recent progress, and current status of atomic frequency standards; promising areas for developing future primary frequency standards; relevance of frequency standards to other areas of metrology including a unified standard concept; statistics of T/F data analysis coupled with the theory and construction of the NBS atomic time scale; an overview of T/F dissemination techniques; and the standards of T/F in the USA. The Monograph addresses both the specialist in the field as well as those desiring basic information about time and frequency.

Complex permittivity and scattering characteristics of forest fire ash particles at microwave and millimetre wave frequencies

The geometric, physical, dynamic and scattering properties of ash particulates resulting from Australian biomass, along with the complex permittivity, have been presented within this dissertation. The rationale behind this work relates to the characterisation of the fundamental scattering properties of ash particulates, with the primary goals being to aid active radar system design and to provide a basic framework for a complex inverse scattering model. The reflectivity coefficient for a volumetrically dispersed medium has been defined by characterising three distinct properties of ash. Firstly, statistical modelling of ash created from various plant and tree species was conducted in order to describe its geometric and material behaviour. Here, similarities between plant and tree species with comparable foliage were noted. Three probability distribution functions (PDF) relating to the projected area, aspect ratio and through thickness dimensions for large ash particles (>0.2mm2) have been mapped. Material investigation has included analysis of the effects of temperature on biomass and the resultant geometric changes this incurs. Furthermore, the effects of natural moisture absorption rates and porosity estimations using measured and micro-computer-tomography (Micro-CT) techniques have been presented. An analysis of the dynamic behaviour of ash particles within a defined volume of space displaying different modes provides the second area of investigation. Particular focus has been given to the ascent and descent phases of the ash particles, with analysis of three dynamic stability modes; namely tumbling, fluttering and chaotic random. Probability distribution functions for orientation and analysis of velocities and Reynolds numbers have been established using video processing techniques. The complex permittivity of ash at both low and high temperatures has been measured. Here, an empirically derived mixing law has been established to theoretically model the complex permittivity of ash. This model also takes into account concentrations of water that may be absorbed by the highly porous material. By applying the knowledge gained from the analysis of ash particles, extensive modelling and measurement work has been carried out to determine their reflectivity. Simulated modelling of the ash has been achieved using a hybrid simulation scheme to accurately implement statistical models over a wide range of frequencies (1-40GHz)

A Multidisciplinary Analysis of Frequency Domain Metal Detectors for Humanitarian Demining

This thesis details an analysis of metal detectors (low frequency electromagnetic induction devices) with emphasis on Frequency Domain (FD) systems and the operational conditions of interest to humanitarian demining. After an initial look at humanitarian demining and a review of their basic principles we turn our attention to electromagnetic induction modelling and to analytical solutions to some basic FD direct (forward) problems. The second half of the thesis focuses then on the analysis of an extensive amount of experimental data. The possibility of target classification is first discussed on a qualitative basis, then quantitatively. Finally, we discuss shape and size determination via near field imaging

Space programs summary no. 37-45, volume IV FOR the period April 1, 1967 to May 31, 1967. Supporting research and advanced development

Space exploration projects on systems, guidance and control, environmental simulation, space sciences, propulsion, telecommunications, and engineering mechanic

Goddard Laboratory for Atmospheric Sciences, collected reprints 1978 - 1979, volume 2

Information about the Earth hydrosphere, obtained in the field and from aircraft and satellite imagery is reported. Particular emphasis is given to the use of microwave sensors in the study of soil moisture, sea ice, snow cover and atmospheric parameters associated with watersheds

Advances in Engineering Science, Volume 3

Papers concerning acoustics, environmental modeling, and energy technology are presented