Signal Processing Commons^™

Gps Multipath Reduction With Correlator Beamforming, Jason M. Barhorst

Theses and Dissertations

This research effort investigates the feasibility of beamforming using a single Global Positioning System (GPS) front end. Traditional methods of beamforming use multiple front ends, typically one per antenna element. By enabling a receiver to sample a switched antenna array, the hardware cost of implementing a GPS antenna array can be significantly reduced. Similar techniques of reducing the number of receivers have been used by Locata Corporation in the design of their non-GPS positioning systems. However, Locata Corporation's local transmitters provide a signal strength much higher than GPS's signal strength. For this reason, the inclusion of low-noise amplifiers into the …

Low-Cost Imu Implementation Via Sensor Fusion Algorithms In The Arduino Environment, Brandon Mccarron

Aerospace Engineering

A multi-phase experiment was conducted at Cal Poly in San Luis Obispo, CA, to design a low-cost inertial measurement unit composed of a 3-axis accelerometer and 3-axis gyroscope. Utilizing the growing microprocessor software environment, a 3-axis accelerometer and 3-axis gyroscope simulated 6 degrees of freedom orientation sensing through sensor fusion. By analyzing a simple complimentary filter and a more complex Kalman filter, the outputs of each sensor were combined and took advantage of the benefits of both sensors to improved results. Gyroscopic drift was removed in the pitch and roll axes using the Kalman filter for both static and dynamic …

An Attitude Determination System With Mems Gyroscope Drift Compensation For Small Satellites, Maxwell Bezold

Theses and Dissertations--Electrical and Computer Engineering

This thesis presents the design of an attitude determination system for small satellites that automatically corrects for attitude drift. Existing attitude determination systems suffer from attitude drift due to the integration of noisy rate gyro sensors used to measure the change in attitude. This attitude drift leads to a gradual loss in attitude knowledge, as error between the estimated attitude and the actual attitude increases.

In this thesis a Kalman filter is used to complete sensor fusion which combines sensor observations with a projected attitude based on the dynamics of the satellite. The system proposed in this thesis also utilizes …

Visual Attitude Propagation For Small Satellites, Samir Ahmed Rawashdeh

Theses and Dissertations--Electrical and Computer Engineering

As electronics become smaller and more capable, it has become possible to conduct meaningful and sophisticated satellite missions in a small form factor. However, the capability of small satellites and the range of possible applications are limited by the capabilities of several technologies, including attitude determination and control systems. This dissertation evaluates the use of image-based visual attitude propagation as a compliment or alternative to other attitude determination technologies that are suitable for miniature satellites. The concept lies in using miniature cameras to track image features across frames and extracting the underlying rotation.

The problem of visual attitude propagation as …

Navigation And Position Determination With A Multicarrier Modulation Signal Of Opportunity, Richard K. Martin, Jamie S. Velotta, John F. Raquet

AFIT Patents

A multicarrier modulation position determination method that includes deploying at least one known receiver with a known location and a second receiver with an unknown location. At least two signals of opportunity with different locations are obtained by both the receiver and the second receiver. The signals having a plurality of block data, the block data having block boundaries. The block boundaries including a beginning block boundary and an end block boundary. The block data further including a cyclic prefix at the beginning block boundary. Acquiring a plurality of data samples for at least a portion of the block data …

Vibration-Based Health Monitoring Of Multiple-Stage Gear Train And Differential Planetary Transmission Involving Teeth Damage And Backlash Nonlinearity, Andrew Patrick Sommer

Master's Theses

The objective of this thesis is to develop vibration-based fault detection strategies for on-line condition monitoring of gear transmission systems. The study divides the thesis into three sections. First of all, the local stresses created by a root fatigue crack on a pinion spur gear are analyzed using a quasi-static finite element model and non-linear contact mechanics simulation. Backlash between gear teeth which is essential to provide better lubrication on tooth surfaces and to eliminate interference is included as a defect and a necessary part of transmission design. The second section is dedicated to fixed axis power trains. Torsional vibration …

Development Of A Cubesat Instrument For Microgravity Particle Damper Performance Analysis, John Trevor Abel

Master's Theses

Spacecraft pointing accuracy and structural longevity requirements often necessitate auxiliary vibration dissipation mechanisms.  However, temperature sensitivity and material degradation limit the effectiveness of traditional damping techniques in space.  Robust particle damping technology offers a potential solution, driving the need for microgravity characterization.   A 1U cubesat satellite presents a low cost, low risk platform for the acquisition of data needed for this evaluation, but severely restricts available mass, volume, power and bandwidth resources.  This paper details the development of an instrument subject to these constraints that is capable of capturing high resolution frequency response measurements of highly nonlinear particle damper dynamics.

Effects Of Cyclic Prefix Jamming Versus Noise Jamming In Ofdm Signals, Amber L. Scott

Theses and Dissertations

Signal jamming of an orthogonal frequency-division multiplexing (OFDM) signal is simulated in MATLAB. Two different means of jamming are used to see, which is a more efficient way to disrupt a signal using the same signal power. The first way is a basic additive white Gaussian noise (AWGN) jammer that equally jams the entire signal. The second way is an AWGN jammer that targets only the cyclic prefix (CP) of the signal. These two methods of jamming are simulated using different channel models and unknowns to get varying results. The three channel models used in the simulations are the no …

Signals Of Opportunity Navigation Using Wi-Fi Signals, Wilfred E. Noel

Theses and Dissertations

Since GPS is generally limited to areas with clear sky view, additional methods of navigation are currently being explored. This thesis explores navigation using Signals of Opportunity(SoOP). The signals chosen for evaluation in this thesis are the common Internet IEEE 802.11a/g signals, or Wi-Fi. This thesis presents SoOP navigation based on cross-correlations of received data from multiple Wi-Fi stations. It shows the effectiveness of the methods using collected Wi-Fi signals in a real-world environment. By using simple statistical representations of collected data in large groups, or windows, cross-correlation calculations can produce timing offsets between simulated stations. The timing offsets, or …

A Shock Tube Technique For Blast Wave Simulation And Studies Of Flow Structure Interactions In Shock Tube Blast Experiments, Nicholas N. Kleinschmit

Department of Engineering Mechanics: Dissertations, Theses, and Student Research

Improvised explosive devices (IED’s) are widely used against US and allied forces fighting in Iraq and Afghanistan. Exposure to IED blast may cause blast-induced traumatic brain injury (bTBI). The injury mechanisms are however not well understood. A critical need in bTBI-related research is the ability to replicate the loading conditions of IED blast waves in a laboratory environment. In this work, experimental studies have been carried out to explore the use of the shock tube technique for generating air shock waves that mimic the temporal and spatial characteristics of free-field blast waves and to investigate the blast wave-test sample interactions …

A 24ft/7.3m Parabolic Reflector Antenna Performance & Feed Design Analysis, Anthony Shelley

Morehead State Theses and Dissertations

A thesis presented to the faculty of the College of Science & Technology at Morehead State University in partial fulfillment of the requirements for the Degree of Master of Science by Anthony Shelley on November 29, 2010.

Scan Loss Pattern Synthesis For Adaptive Array Ground Stations, William C. Barott, Mary Ann Ingram, Paul G. Steffes

Publications

We present several techniques for maximizing the contact time between low Earth orbiting satellites (LEOs) and a ground station (GS). The GS comprises an adaptive array of electronically steered space-fed lenses (SFLs). Each SFL is manufactured as a low-cost printed circuit with the result that it exhibits scanning loss. By differently orienting the boresights of the SFLs in the adaptive array, the SFL's scanning losses can be made to optimally complement the path loss of the LEO, thereby reducing the cost of the GS while maximizing the download capacity of the satellite link. The optimization, implemented with a genetic algorithm …

Aiding Gps With Additional Satellite Navigation Services, Yasin A. Mutlu

Theses and Dissertations

In modern warfare navigation services are very important. GPS is currently providing service for accurate navigation, except in some areas, especially urban areas, where GPS signals cannot always be tracked by users. In these cases some additional navigation support could be provided by other global navigation satellite systems. If GPS is combined with other navigation systems than the navigation gap will be minor. In this thesis, the effect of combining GPS with other satellite navigation systems, specifically GLONASS, Galileo and Compass, is evaluated in terms of availability and position dilution of precision (PDOP) values. First, satellite constellations are simulated in …

Real-Time On-Board Object Tracking For Cooperative Flight Control, Ajay Kumar Mandava, Emma Regentova, Henry Selvaraj

Electrical & Computer Engineering Faculty Research

One of possible cooperative Situations for flights could be a scenario when the decision on a new path is taken by A Certain fleet member, who is called the leader. The update on the new path is Transmitted to the fleet members via communication That can be noisy. An optical sensor can be used as a back-up for re-estimating the path parameters based on visual information. For A Certain topology, the issue can be solved by continuous tracking of the leader of the fleet in the video sequence and re-adjusting parameters of the flight, accordingly. To solve such a problem …

Failure Detection Of A Pseudolite-Based Reference System Using Residual Monitoring, Michael A. Ciampa

Theses and Dissertations

The 746th TS uses a flight reference system referred to as the Central Inertial and GPS Test Facility (CIGTF) Reference System (CRS). Currently the CRS is the modern standard flight reference system for navigation testing, but high accuracy is dependent on the availability of GPS. A pseudolite system is currently being developed to augment the CRS and supply the capability to maintain high accuracy navigation under normal and jamming conditions. Pseudolite measurements typically contain cycle slips and other errors (such as multipath, tropospheric error, measurement noise) that can affect reliability. Past work relied on the receiver-reported signal-to-noise (SNR) value to …

Fusion Of Inertial Sensors And Orthogonal Frequency Division Multiplexed (Ofdm) Signals Of Opportunity For Unassisted Navigation, Jason G. Crosby

Theses and Dissertations

The advent of the global positioning system (GPS) has provided worldwide high-accuracy position measurements. However, GPS may be rendered unavailable by jamming, disruption of satellites, or simply by signal shadowing in urban environments. Thus, this thesis considers fusion of Inertial Navigation Systems (INS) and Orthogonal Frequency Division Multiplexed (OFDM) signals of opportunity (SOOP) for navigation. Typical signal of opportunity navigation involves the use of a reference receiver and uses time difference of arrival (TDOA) measurements. However, by exploiting the block structure of OFDM communication signals, the need for the reference receiver is reduced or possibly removed entirely. This research uses …

Antennas For Portable Communications In The Uwb And Gps Spectra., Giuseppe Ruvio

Doctoral

The thesis describes a study of antennas for solutions in emerging systems. An account of the fundamental principles of these antennas is given together with an outline of the basic electromagnetic theory on which the designs are based. While the main focus is on antennas for Ultra Wideband (UWB) systems, some additional work was carried out on enhancing performance of circularly polarised antennas for satellite navigation systems. The study focussed on the design of highly efficient broadband antennas with particular requirements for size compactness, gain stability, phase-linearity, and the use of low-cost materials. These requirements are particularly important for UWB …

Navigation Using Orthogonal Frequency Division Multiplexed Signals Of Opportunity, Jamie S. Velotta

Theses and Dissertations

The global positioning system (GPS) provides high-accuracy position measurements anywhere in the world. However, a limitation of this system is that a line of sight to multiple satellites is required; therefore, it is unsuitable to use indoors or in urban canyons. Also, in the presence of radio-frequency interference or jamming, GPS may be unavailable. Alternative methods of navigation and positioning are need to either compliment GPS as a backup or for use in areas unreachable by satellites. This research analyzes a feature-based correlation approach for determining reception differences between two Orthogonal Frequency Division receivers for the purpose of TDOA calculations. …

A Small-Scale 3d Imaging Platform For Algorithm Performance Evaluation, Steven A. James

Theses and Dissertations

In recent years, world events have expedited the need for the design and application of rapidly deployable airborne surveillance systems in urban environments. Fast and effective use of the surveillance images requires accurate modeling of the terrain being surveyed. The process of accurately modeling buildings, landmarks, or other items of interest on the surface of the earth, within a short lead time, has proven to be a challenging task. One approach of high importance for countering this challenge and accurately reconstructing 3D objects is through the employment of airborne 3D image acquisition platforms. While developments in this arena have significantly …

Reconstructing Spectral Scenes Using Statistical Estimation To Enhance Space Situational Awareness, Travis F. Blake

Theses and Dissertations

A new sensor, the Advanced Electro-Optical System (AEOS) Spectral Imaging Sensor (ASIS) has been developed at the Maui Space Surveillance Complex (MSSC). ASIS is capable of collecting resolved imagery of space objects in 10's-100's of spectral bands while using an adaptive optics system. However, the stringent requirements of collecting ground-based images requires a sensor that induces spectral blurring. Post-processing algorithms to remove this blurring are required to fully exploit these spectral images. This research focuses on developing the reconstruction algorithms, based on proven estimation theories, required to spectrally deblur the images collected from ASIS. Additionally, the research will expand the …

Lightweight In-Plane Actuated Deformable Mirrors For Space Telescopes, Michael J. Shepherd

Theses and Dissertations

This research focused on lightweight, in-plane actuated, deformable mirrors, with the ultimate goal of developing a 20- meter light gathering aperture for space telescopes. The 0.127 meter diameter deformable mirror small scale testbed was modelled infinite elements using MSC.Nastran software and then used as a basis for a quasi-static controller. Experimental tracking of Zernike tip, tilt, and defocus modes was accomplished. The analytical solutions to plate-membrane and beam-string ordinary differential equations were developed. A simplified approach to modelling the axisymmetric cases was also presented. A novel static control strategy, the Modal Transformation Method, was developed to form Zernike surfaces within …

Navigation Using Signals Of Opportunity In The Am Transmission Band, Jonathan A. Mcellroy

Theses and Dissertations

Maintaining a precision navigation solution both in a GPS hostile jamming environment and also in a GPS non-compatible terrain area is of great importance. To that end, this thesis evaluates the ability to navigate using signals from the AM band of the electromagnetic spectrum (520 to 1710 kHz). Navigation position estimates are done using multi-lateration techniques similar to GPS. However, pseudoranges are created using Time Difference of Arrival (TDOA) distances between a reference receiver and a mobile receiver, allowing the mobile receiver to obtain absolute position estimates over time. Four methods were developed for estimating the cross-correlation peak within a …

Fusion Of Imaging And Inertial Sensors For Navigation, Michael J. Veth

Theses and Dissertations

The motivation of this research is to address the limitations of satellite-based navigation by fusing imaging and inertial systems. The research begins by rigorously describing the imaging and navigation problem and developing practical models of the sensors, then presenting a transformation technique to detect features within an image. Given a set of features, a statistical feature projection technique is developed which utilizes inertial measurements to predict vectors in the feature space between images. This coupling of the imaging and inertial sensors at a deep level is then used to aid the statistical feature matching function. The feature matches and inertial …

Laser Covariance Vibrometry For Unsymmetrical Mode Detection, Michael C. Kobold

Theses and Dissertations

Simulated cross - spectral covariance (CSC) from optical return from simulated surface vibration indicates CW phase modulation may be an appropriate phenomenology for adequate classification of vehicles by structural mode. The nonlinear structural to optical relationship is close to unity, avoiding nulls and high values; optical return contains sufficient spectral ID information necessary for data clustering. The FE model has contact between the homogeneous rolled armor and vehicle hull, a simple multi - layer skin model typical of most vehicles. Most of the high frequency energy moved to lower frequencies. This nonlinearity segments contact vibration modes into two classes: symmetrical …

Space-Time Adaptive Processing For Side-Looking Arrays With Platform Maneuver, John T. Buckreis

Theses and Dissertations

This research effort develops a space-time adaptive processing (STAP) radar data model for the side-looking (SL) array with platform maneuver. A primary assumption of most STAP models is the absence of platform maneuver during the coherent processing interval (CPI). This research abandons the platform stationarity assumption, allowing platform pitch, roll, and yaw during the CPI. The model developed characterizes platform maneuver effects on the clutter spectrum, examines Matched Filter (MF) output Signal-to-Interference-plus-Noise-Ratio (SINR), and investigates maneuver impact on sample support homogeneity. The introduction of pitch marginally impacts MF SINR due to the lack of achieved azimuth resolution in this research, …

Evaluating The Correlation Characteristics Of Arbitrary Am And Fm Radio Signals For The Purpose Of Navigation, Bryan S. Kim

Theses and Dissertations

The Global Positioning System (GPS) provides position estimates on the Earth at anytime, anywhere and in any weather. However, to provide robust positioning, GPS requires an unobstructed path to satellite signals. As such, GPS performance generally degrades or becomes non-existent in environments such as large urban areas. This research investigates and analyzes the correlation characteristics of arbitrary AM and FM radio signals for the purpose of navigation. Simulations are conducted with different combinations of correlation methods (`fixed' or `varying'), modulation types (AM or FM), and signal types (song or voice). Out of the eight different variations considered, only two provided …

Variable Structure Control Of Unsteady Nonlinear Aeroelastic System, With Partial State Information, Sushma Gujjula, Sahjendra N. Singh

Electrical & Computer Engineering Faculty Research

This paper treats the question of control of a two-degree-of-freedom unsteady aeroelastic system with partial state information in the presence of uncertainties. The chosen model describes the plunge and pitch motion of a wing and a single trailing-edge control surface is utilized for the purpose of control. Based on the Lyapunov approach, a variable structure control law is derived. For the control law derivation, the system is treated as the interconnection of two subsystems in which the subsystem associated with the unsteady aerodynamics is input-to-state stable. The stability property of this subsystem is exploited to generate a dominating signal for …

Electromagnetic Propagation Prediction Inside Aircraft Cabins, Genevieve Hankins

Electrical & Computer Engineering Theses & Dissertations

Electromagnetic propagation models for signal strength prediction within aircraft cabins are essential for evaluating and designing a wireless communication system to be implemented onboard aircraft. There are many commercially available software packages for predicting wireless system performance in conventional indoor environments. It is of interest to examine the available software to determine if the aircraft's electromagnetic environment (EME) can be modeled successfully without developing an aircraft specific prediction tool. EnterprisePlanner®, a registered product of Wireless Valley Communications, Incorporated, was selected for the present effort. The performance of the prediction model was evaluated through a comparison with field measurements taken on …

Electromagnetic Wave Propagation Prediction For Wireless Networks Inside Boeing Fuselages, Mennatoallah Youssef

Electrical & Computer Engineering Theses & Dissertations

Commercial grade software is intended for electromagnetic predictions within office buildings; it was used to develop models to analyze propagation inside airplane fuselages. This study shows that Wireless XGTD and Insite software can accurately predict power propagation within airplane fuselages. Current work uses fuselage models, which contain additional internal components. A comparison was made between empty and full fuselage to examine the effects of internal components. Two propagation model types [Fast 3D and Full 3D] were also compared for accuracy to experimental study. It was concluded that completed fuselages are suggested for further simulation study as well as that the …

The Use Of X-Ray Pulsars For Aiding Gps Satellite Orbit Determination, Dennis W. Woodfork Ii

Theses and Dissertations

This research proposes the use of an existing "signal of opportunity" - namely x-ray pulsars - to improve the accuracy and robustness of the GPS satellite and clock estimation algorithm. Improvement in satellite and clock accuracy results in a direct benefit to the user. A simulation has been developed to determine the effects of using x-ray pulsar measurements on the GPS Operational Control Segment. The epoch-specific position, velocity, and clock errors of all GPS satellites in the constellation were estimated using both pseudoranges and time-difference-of-arrival (TDOA) measurements from pulsars. The primary measure of accuracy is a constellation Signal-In-Space Range Error …