Waveform-Domain Adaptive Matched Filtering: A Novel Approach to Suppressing Interrupted-Sampling Repeater Jamming

The inadequate adaptability to flexible interference scenarios remains an unresolved challenge in the majority of techniques utilized for mitigating interrupted-sampling repeater jamming (ISRJ). Matched filtering system based methods is desirable to incorporate anti-ISRJ measures based on prior ISRJ modeling, either preceding or succeeding the matched filtering. Due to the partial matching nature of ISRJ, its characteristics are revealed during the process of matched filtering. Therefore, this paper introduces an extended domain called the waveform domain within the matched filtering process. On this domain, a novel matched filtering model, known as the waveform-domain adaptive matched filtering (WD-AMF), is established to tackle the problem of ISRJ suppression without relying on a pre-existing ISRJ model. The output of the WD-AMF encompasses an adaptive filtering term and a compensation term. The adaptive filtering term encompasses the adaptive integration outcomes in the waveform domain, which are determined by an adaptive weighted function. This function, akin to a collection of bandpass filters, decomposes the integrated function into multiple components, some of which contain interference while others do not. The compensation term adheres to an integrated guideline for discerning the presence of signal components or noise within the integrated function. The integration results are then concatenated to reconstruct a compensated matched filter signal output. Simulations are conducted to showcase the exceptional capability of the proposed method in suppressing ISRJ in diverse interference scenarios, even in the absence of a pre-existing ISRJ model

Amplitude and phase sonar calibration and the use of target phase for enhanced acoustic target characterisation

This thesis investigates the incorporation of target phase into sonar signal processing, for enhanced information in the context of acoustical oceanography. A sonar system phase calibration method, which includes both the amplitude and phase response is proposed. The technique is an extension of the widespread standard-target sonar calibration method, based on the use of metallic spheres as standard targets. Frequency domain data processing is used, with target phase measured as a phase angle difference between two frequency components. This approach minimizes the impact of range uncertainties in the calibration process. Calibration accuracy is examined by comparison to theoretical full-wave modal solutions. The system complex response is obtained for an operating frequency of 50 to 150 kHz, and sources of ambiguity are examined. The calibrated broadband sonar system is then used to study the complex scattering of objects important for the modelling of marine organism echoes, such as elastic spheres, fluid-filled shells, cylinders and prolate spheroids. Underlying echo formation mechanisms and their interaction are explored. Phase-sensitive sonar systems could be important for the acquisition of increased levels of information, crucial for the development of automated species identification. Studies of sonar system phase calibration and complex scattering from fundamental shapes are necessary in order to incorporate this type of fully-coherent processing into scientific acoustic instruments

A Nonparametric Approach to Segmentation of Ladar Images

The advent of advanced laser radar (ladar) systems that record full-waveform signal data has inspired numerous inquisitions which aspire to extract additional, previously unavailable, information about the illuminated scene from the collected data. The quality of the information, however, is often related to the limitations of the ladar camera used to collect the data. This research project uses full-waveform analysis of ladar signals, and basic principles of optics, to propose a new formulation for an accepted signal model. A new waveform model taking into account backscatter reflectance is the key to overcoming specific deficiencies of the ladar camera at hand, namely the ability to discern pulse-spreading effects of elongated targets. A concert of non-parametric statistics and familiar image processing methods are used to calculate the orientation angle of the illuminated objects, and the deficiency of the hardware is circumvented. Segmentation of the various ladar images performed as part of the angle estimation, and this is shown to be a new and effective strategy for analyzing the output of the AFIT ladar camera

Time-to-passage estimation on periphery : better for biological motion?

In  previous  studies,  complex  motion  stimuli  were  judged  as  passing  sooner  than  rigid stimuli  but  reflected  more  uncertainty  in  the  judgments  as  revealed  by  precision  loss  and  longer reaction  times.  It  is  known  that  biological  motion  can  be  perceived  in  the  periphery .  In  the everyday  life  people  are  required  to  interact  with  or  to  estimate  motion  variables  of  other  agents located  on  the  periphery ,  at  different  locations  of  the  visual  field.  In  this  study ,  stimuli  were presented  in  different  peripheral  location  (16°,  32°  and  48°).  In  a  time-­to-­passage  (TTP)  task  rigid (RM),  biological  (BM)  and  scrambled  (SM)  motion  conditions  were  compared.  Seven  simulated velocities  were  combined  with  seven  starting  distances,  resulting  in  49  levels  of  TTP:  24 conditions  that  arrived  before  1s  and  24  that  arriving  after  1s.  Subjects  had  to  decide  whether the  point-‐‑light  walker  (PLW)  passed  the  eye  plane  before  or  after  a  reference  time  (1s)  signaled by  a  tone.  Subjects  could  judge  time  to  passage  of  PLW  peripherally  to  an  eccentricity  of  at  least 48o.  Judgments  for  complex  motion  patterns  (BM  and  SM)  showed  an  anticipation  of  the passage  combined  with  a  loss  of  precision  when  compared  with  RM,  at  eccentricity  16o.  The effect  of  eccentricity  on  precision  was  revealed  by  the  increase  of  SD  along  eccentricities  for SM.  The  TTP  judgment  seemed  to  become  less  precise  as  the  stimuli  were  displaced  farther along  the  peripheral  field.  For  BM,  an  improvement  on  precision  was  verified  at  eccentricity  32o, and  a  subsequent  deterioration  just  at  eccentricity  48o.  The  anticipation  of  the  passage  for  BM was  no  longer  found  on  periphery ,  while  the  differences  on  the  precision  between  BM  and  RM vanished.Fundação para a Ciência e a Tecnologia (FCT

NASA Tech Briefs, May 2012

Topics covered include: An "Inefficient Fin" Non-Dimensional Parameter to Measure Gas Temperatures Efficiently; On-Wafer Measurement of a Multi-Stage MMIC Amplifier with 10 dB of Gain at 475 GHz; Software to Control and Monitor Gas Streams; Miniaturized Laser Heterodyne Radiometer (LHR) for Measurements of Greenhouse Gases in the Atmospheric Column; Anomaly Detection in Test Equipment via Sliding Mode Observers; Absolute Position of Targets Measured Through a Chamber Window Using Lidar Metrology Systems; Goldstone Solar System Radar Waveform Generator; Fast and Adaptive Lossless Onboard Hyperspectral Data Compression System; Iridium Interfacial Stack - IrIS; Downsampling Photodetector Array with Windowing; Optical Phase Recovery and Locking in a PPM Laser Communication Link; High-Speed Edge-Detecting Line Scan Smart Camera; Optical Communications Channel Combiner; Development of Thermal Infrared Sensor to Supplement Operational Land Imager; Amplitude-Stabilized Oscillator for a Capacitance-Probe Electrometer; Automated Performance Characterization of DSN System Frequency Stability Using Spacecraft Tracking Data; Histogrammatic Method for Determining Relative Abundance of Input Gas Pulse; Predictive Sea State Estimation for Automated Ride Control and Handling - PSSEARCH; LEGION: Lightweight Expandable Group of Independently Operating Nodes; Real-Time Projection to Verify Plan Success During Execution; Automated Performance Characterization of DSN System Frequency Stability Using Spacecraft Tracking Data; Web-Based Customizable Viewer for Mars Network Overflight Opportunities; Fabrication of a Cryogenic Terahertz Emitter for Bolometer Focal Plane Calibrations; Fabrication of an Absorber-Coupled MKID Detector; Graphene Transparent Conductive Electrodes for Next- Generation Microshutter Arrays; Method of Bonding Optical Elements with Near-Zero Displacement; Free-Mass and Interface Configurations of Hammering Mechanisms; Wavefront Compensation Segmented Mirror Sensing and Control; Long-Life, Lightweight, Multi-Roller Traction Drives for Planetary Vehicle Surface Exploration; Reliable Optical Pump Architecture for Highly Coherent Lasers Used in Space Metrology Applications; Electrochemical Ultracapacitors Using Graphitic Nanostacks; Improved Whole-Blood-Staining Device; Monitoring Location and Angular Orientation of a Pill; Molecular Technique to Reduce PCR Bias for Deeper Understanding of Microbial Diversity; Laser Ablation Electrodynamic Ion Funnel for In Situ Mass Spectrometry on Mars; High-Altitude MMIC Sounding Radiometer for the Global Hawk Unmanned Aerial Vehicle; PRTs and Their Bonding for Long-Duration, Extreme-Temperature Environments; Mid- and Long-IR Broadband Quantum Well Photodetector; 3D Display Using Conjugated Multiband Bandpass Filters; Real-Time, Non-Intrusive Detection of Liquid Nitrogen in Liquid Oxygen at High Pressure and High Flow; Method to Enhance the Operation of an Optical Inspection Instrument Using Spatial Light Modulators; Dual-Compartment Inflatable Suitlock; Large-Strain Transparent Magnetoactive Polymer Nanocomposites; Thermodynamic Vent System for an On-Orbit Cryogenic Reaction Control Engine; Time Distribution Using SpaceWire in the SCaN Testbed on ISS; and Techniques for Solution- Assisted Optical Contacting

Investigation of continuous-wave range-resolved lidar systems for gas detection and concentration measurement

The techniques for detection of the atmosphere constituents and their distribution in the space have evolved in the last years driven by needs in the environmental, meteorological and climate science fields and backed by technological developments. The study of the atmosphere behavior, the health risks provoked either by natural or man-made phenomena or the study of the climate change are examples of applications of optical remote sensing techniques that tend to increase as time goes by. This thesis presents an innovative lidar system for gas detection with range resolution and moderate cost. We study a frequency-modulated continuous-wave lidar system (FMCW) for gas detection in the atmosphere. As a previous step a system for aerosol detection has been studied, which has led to the development of a phase switching technique in the modulating signal to make possible the retrieval of the low-spatial-frequency components of the atmosphere optical parameters. This technique has been tested with an experiment of discrimination of targets close to each other. Then the system has been extended to gas detection either with topographical targets or with aerosols as backscattering medium and a preliminary experiment for the first case has been performed. An analysis of the uncertainty in the gas-concentration retrieval as a function of the signal-to-noise ratio (SNR) has been developed and the extension of the `phase-hop¿ technique for gas-detection FMCW-lidar systems has been proposed. Previous to this system, a wavelength modulation spectroscopy (WMS) system has been developed as an intermediate step to achieve some degree of expertise in gas detection by means of absorption spectroscopy techniques. Different experiments with gas cells and open-path environments have been carried out. Finally an optical amplifier which can be used in WMS systems as well as in FMCW-lidar systems is studied, designed, developed and tested. The analysis of the fiber-amplifier behavior for conditions of temperature and pressure change has been performed with a certain dependence of the background with temperature.Les tècniques per a la detecció dels constituents de l’atmosfera i la seva distribució en l’espai ha evolucionat en els últims anys degut a les necessitats en els camps del medi ambient, la meteorologia i les ciències del clima i amb el suport del desenvolupament tecnològic. L’estudi del comportament atmosfèric, els riscos per la salut provocats per fenòmens tant naturals com artificials o l’estudi del canvi climàtic són exemples d’aplicacions de tècniques de teledetecció òptica que tendeixen a incrementar amb el temps. Aquesta tesi presenta un sistema lidar innovador per a la detecció de gasos amb resolució en distancia i amb un cost moderat. S’estudia un sistema lidar d’ona continua i modulat en freqüència FMCW (frequency-modulated continuous-wave) per a la detecció de gasos a l’atmosfera. Com a pas previ, s’ha estudiat un sistema per a detecció d’aerosols que ha portat al desenvolupament d’una tècnica de salts de fase en el senyal modulador per tal de fer possible la recuperació dels components de baixa freqüència espacial dels paràmetres òptics atmosfèrics. Aquesta tècnica s’ha testejat amb un experiment de discriminació de blancs propers entre ells. Llavors el sistema s’ha estès a la detecció de gasos utilitzant com a medi de retrodispersió tant els blancs topogràfics com els aerosols i s’ha fet un experiment preliminar per al primer cas de blancs topogràfics. S’ha analitzat també la incertesa en la recuperació de la concentració de gas com a funció de la relació senyal-soroll (SNR) i s’ha proposat l’extensió de la tècnica phase-hop per a sistemes lidar FMCW per a la detecció de gasos. Previ a aquest sistema, s’ha desenvolupat un sistema WMS (wavelength modulation spectroscopy) com a pas intermedi per tal d’assolir un cert grau d’expertesa en la detecció de gasos per mitjà de tècniques d’absorció espectroscòpica. S’han desenvolupat diferents experiments amb cel·les de gas i també en espais oberts. Finalment s’ha estudiat, dissenyat, desenvolupat i testejat un amplificador òptic que es pot fer servir en sistemes WMS així com en sistemes lidar FMCW. L’anàlisi del comportament de l’amplificador de fibra per a condicions de canvi de pressió i temperatura s’ha realitzat obtenint com a resultat una certa dependència del senyal de background amb la temperatura.Postprint (published version

Development of GPR data analysis algorithms for predicting thin asphalt concrete overlay thickness and density

Thin asphalt concrete (AC) overlay is a commonly used asphalt pavement maintenance strategy. The thickness and density of thin AC overlay are important to achieving proper pavement performance, which can be evaluated using ground-penetrating radar (GPR). The traditional methods for predicting pavement thickness and density relies on the accurate determination of electromagnetic (EM) signal reflection amplitude and time delay. Due to the limitation of GPR antenna bandwidth, the range resolution of the GPR signal is insufficient for thin pavement layer evaluation. To this end, the objective of this study is to develop signal processing techniques to increase the resolution of GPR signals, such that they can be applied to thin AC overlay evaluation. First, the generic GPR forward 2-D imaging scheme is discussed. Then two linear inversion techniques are proposed, including migration and sparse reconstruction. Both algorithms were validated on GPR signals reflected from buried pipes using finite difference time domain (FDTD) simulation. Second, as a special case of the 2-D GPR imaging and linear inversion reconstruction, regularized deconvolution was applied to GPR signals reflected from thin AC overlays. Four types of regularization methods, including Tikhonov regularization and total variation regularization, were compared in terms of accuracy in estimating thin pavement layer thickness. The L-curve method was used to identify the appropriate regularization parameter. A subspace method—a multiple signal classification (MUSIC) algorithm—was then utilized to increase the resolution of 3-D GPR signals. An extended common midpoint (XCMP) method was used to find the dielectric constant and the thickness of the thin AC overlay at a full-scale test section. The results show that the MUSIC algorithm is an effective approach for increasing the 3-D GPR signal range resolution when the XCMP method is applied on thin AC overlay. Furthermore, a non-linear inversion technique is proposed based on gradient descent. The proposed non-linear optimization algorithm was applied on real GPR data reflected from thin AC overlay and the thickness and density prediction results are accurate. Finally, a “modified reference scan” approach was developed to eliminate the effect of AC pavement surface moisture on GPR signals, such that the density of thin AC overlay can be monitored in real time during compaction