ITC/USA 2013 Conference Proceedings / The Forty-Ninth Annual International Telemetering Conference and Technical Exhibition / October 21-24, 2013 / Bally's Hotel & Convention Center, Las Vegas, NV / Telemetry ground stations spread over geographically diverse areas are well suited for use in passively locating the source of a distant transmitted signal. In a favorable positioning of receive sites, the accuracy of these passive localization techniques can compete with the accuracy of radars. In these cases, use of receive only assets is a less expensive alternative than the use of a radar's scarce resources. Until recently, the major technical challenge to implementation of the passive localization techniques of time-difference of arrival (TDOA) and frequency-difference of arrival (FDOA) has been the frequency and time stability of geographically separated receivers. Advances in GPS based timing and frequency references has made the implementation of TDOA and FDOA feasible. This paper shows how these limitations have been overcome using the current telemetry assets at the Reagan Test Site in Kwajalein Atoll.

As CMOS technologies advance to 22-nm dimensions and below, constructing analog circuits are difficult to design within permitted specifications. One of the reasons for this is a limit of voltage resolution. In this situation, time-mode processing is a technique that is believed to be well suited for solving many of these challenges. A primary advantage of this technique is the ability to achieve analog functions using digital logic structures. Time difference amplifiers (TDA) can be a key component to realize fine time solutions. TDA are an innovative method to improve the time resolution as well as the evolution of ADC. This thesis introduces a TDA that amplifies the input time difference between two signals by a fractional gain. The closed loop gain control system used in this work consists of a pseudo differential current starved delay element (PDCSDE) and a monotonic digitally controlled delay element (DCDE). By using these elements to create a delay chain and a control loop, the result is a stable fractional time difference gain (TD gain). The system was designed and simulated in 65nm process at 1.2V power supply. The measured results show that this TDA achieves a fractional TD gain offset lower than 1.3%, with supply variation of ±15%, and input range as wide as ±250ps. The new design was also more resilient to process, voltage and temperature (PVT) variations

<p>This thesis considers passive localization and tracking. Here, passive refers to passive observations - the type of observations for which the full position estimate of the target cannot be obtained using a single measurement, like those are from a sonar. Hence, localizing or tracking targets based on these measurements calls for the use of multiple sensors. This poses a different set of challenges to tracking with passive observations as opposed to active observations where full target position is available from a single measurement.</p><p>We identify different issues that are related to passive localization and tracking and propose algorithmic solutions to these problems. We consider the angle of arrival (AOA), which is the passive measurement that is often considered in target tracking and time difference of arrival (TDOA) as representative passive measurements to illustrate our algorithms. Whereas, the AOA measurements from different sensors can be considered independent, TDOA measurements, on the other hand, are not independent. That is, they are correlated. We would, however, like to note that the proposed algorithms can be applied with straightforward, but simple, modifications to other types of passive measurements.</p><p>In particular, this thesis provides solutions to the following problems. First, it provides efficient and improved algorithms to the data association problem when tracking with multiple passive synchronous sensors. These solutions are based on the assignment formulation. Whereas one of the algorithms proposed, the gated assignment algorithm, uses the validation gates to reduce the computational cost, the other is a new extension to the multidimensional assignment algorithm that associates the measurements directly to the tracks. This is called the (S + 1)-D assignment-based data association, where S is the number of synchronous sensors available in the tracking system. An approximation to this new (S + 1)-D algorithm is also presented.</p> <p> In literature one finds algorithms to localize a single target using TDOA measurements. None of these algorithms considered the issues that might arise in tracking the localized targets. This thesis provides a framework to localize and track targets based on TDOA measurements. The localization algorithm uses a formulation based on the sensor-emitter geometry. This formulation is considered as a constrained optimization problem and two relaxation-based algorithms are provided to solve this optimization problem. The assignment-based data association provides an additional challenge because the TDOA measurements are correlated. This problem is identified and a solution is provided by modifying the calculation of the association cost.</p> <p> Finally, this thesis also provides an efficient algorithm to form AOA mono tracks using the fast Fourier transform (FFT) and the assignment algorithm. Formation of the mono tracks is very useful in distributed tracking and is the well-known direction of arrival tracking problem in the signal processing community.</p> / Thesis / Doctor of Philosophy (PhD)

In this thesis, a complete localization system using asynchronous time difference of arrival (A-TDOA) technique has been thoroughly studied from concept to implementation. The work spans from a proposal of a new A-TDOA system deployment and modeling, through a derivation of the achievable estimation bound, to estimation algorithms development, to a hardware realization, and ultimately to measurements conducted in realistic radio environments. The research begins with a new deployment of an A-TDOA localization system. Compared to the conventional time of arrival (TOA) and time difference of arrival (TDOA) systems, it does not require clock synchronization within the network, which enables a flexible and fast deployment. When deployed in the simplest form, it can effectively reduce system complexity and cost, whereas if all anchor nodes are equipped with full transmit and receive capability, the A-TDOA system can achieve superior performance using a novel receiver re-selection technique. Determining the physical position of a target node in a noisy environment is critical. In this thesis, two novel algorithms, namely, a two-step and a constrained least squares (CLS) algorithms, are proposed offering excellent accuracy and the best trade-off between complexity and precision respectively. The two-step algorithm exploits the advantages of the semi-definite programming (SDP) and the Taylor method, i.e., global convergence and high precision, to achieve superior performance. The CLS algorithm significantly reduces the computation complexity while achieving good accuracy. Despite extensive research efforts on ranging and localization modeling and simulation, knowledge about practical implementations is limited. For the first time, a complete prototype based on A-TDOA technique is implemented in hardware. All sub-systems are developed from scratch and undergone significant modifications for improved reliability. The design objective is low cost and low complexity, and therefore a non-coherent receiver architecture was adopted. The target node design is based on receive and re-transmit technique and is prototyped in analog domain to avoid clock offset and skews. The implemented system has been extensively tested in an outdoor and indoor radio environments. The accuracy obtained are 20.7 cm and 15.2 cm respectively. Comparison with the literature published up to date proves the excellent quality of the design and implementation. To better understand the localization accuracy, the error sources due to thermal noise, hardware limitation, radio propagation channel and clock jitter are identified and investigated. Mitigation methods are proposed to reduce errors. / Graduate

The main crux of this thesis was to produce a model that was capable of simulating the theoretical performance of different configurations for a spatial measurement system using radio frequency technology. It has been important to study new modalities of spatial measurement since spatial measurement systems are an enabling technology that have allowed for the creation of better medical procedures and techniques, provided valuable data for motion capture in animation and biomechanics, and have improved the quality of manufacturing processes in many industries. However, there has been room for improvement in the functional design and accuracy of spatial measurement systems that will enhance current applications and further develop new applications in medicine, research and industry. <br /><br /> In this thesis, a modelling framework for the investigation of spatial measurement based on radio frequency signals was developed. The simulation framework was designed for the purpose of investigating different position determination algorithms and sensor geomatries. A finite element model using the FEMLAB partial differential equation modelling tool was created for a time-domain model of electromagnetic wave propagation in order to simulate the radio frequency signals travelling from a transmitting source antenna to a set of receiving antenna sensors. Electronic line signals were obtained using a simple receiving infinitesimal dipole model and input into a time difference of arrival localization algorithm. The finite element model results were validated against a set of analytical solutions for the free space case. The accuracy of the localization algorithm was measured against a set of possible applications for a potential radio frequency spatial measurement system design. <br /><br /> It was concluded that the simulation framework was successful should one significant deficiency be corrected in future research endeavours. A phase error was observed in the signals extracted at the receiving antenna locations. This phase error, which can be up to 40??, was attributed to the zeroth order finite elements implemented in the finite element model. This phase error can be corrected in the future if higher order vector elements are introduced into future versions of FEMLAB or via the development of custom finite element analysis software but were not implemented in this thesis due to time constraints. Other improvements were also suggested for future work.

This paper involves the calculation for composition of different layer used in laser structure and the simulation of cavity, formed by creating air columns in the InGaAsP medium, for square lattice. The aim of this project is to fabricate approximately zero threshold current lasers. This project involves FDTD simulation for optimizing dimension of the device, fabrication of laser structure and finally characterization of the device structure. / Singapore-MIT Alliance (SMA)

In the current era of telecommunication the usage of cellular network has increased rapidly. Number of different new services are introduced i.e. navigation, friend finder, internet browsing, nearby filling stations, shopping centers, traffic information and emergency services. Most of these services are location based and needs the information of particular area to provide the exact services. The addition of location based services in 3G network opens the new ways of using Mobile devices due to which cellular networks has faced number of challenges in providing better positioning accuracy which is the main requirement for location based services. To bear these challenges everyday new ways of finding the accurate position are introduced but most them required upgraded networks or highly equipped terminal. In this thesis the purpose is to find the potential in UMTS signaling data to estimate the position of the user equipment as accurate as possible using the legacy terminals. In this thesis SFN-SFN observed time difference is explored and used in Database Correlation Method (DCM) in network based positioning. This thesis is done by first analyzing the RSCP for the particular area to verify the conditions of FCC. The data is collected in real environment through test drive using TEMS investigation tool and the available measurement reports from the terminal are used to design and implement the DCM Algorithm. Two new approaches are introduced in this thesis SFN-SFN OTD and Hybrid. In Hybrid RSCP and SFN-SFN OTD are used together. In conclusion, the final results from the performed experiments show improvement in estimated position accuracy by Hybrid technique which is a new step in finding the position of user equipment by DCM.

The main crux of this thesis was to produce a model that was capable of simulating the theoretical performance of different configurations for a spatial measurement system using radio frequency technology. It has been important to study new modalities of spatial measurement since spatial measurement systems are an enabling technology that have allowed for the creation of better medical procedures and techniques, provided valuable data for motion capture in animation and biomechanics, and have improved the quality of manufacturing processes in many industries. However, there has been room for improvement in the functional design and accuracy of spatial measurement systems that will enhance current applications and further develop new applications in medicine, research and industry. <br /><br /> In this thesis, a modelling framework for the investigation of spatial measurement based on radio frequency signals was developed. The simulation framework was designed for the purpose of investigating different position determination algorithms and sensor geomatries. A finite element model using the FEMLAB partial differential equation modelling tool was created for a time-domain model of electromagnetic wave propagation in order to simulate the radio frequency signals travelling from a transmitting source antenna to a set of receiving antenna sensors. Electronic line signals were obtained using a simple receiving infinitesimal dipole model and input into a time difference of arrival localization algorithm. The finite element model results were validated against a set of analytical solutions for the free space case. The accuracy of the localization algorithm was measured against a set of possible applications for a potential radio frequency spatial measurement system design. <br /><br /> It was concluded that the simulation framework was successful should one significant deficiency be corrected in future research endeavours. A phase error was observed in the signals extracted at the receiving antenna locations. This phase error, which can be up to 40°, was attributed to the zeroth order finite elements implemented in the finite element model. This phase error can be corrected in the future if higher order vector elements are introduced into future versions of FEMLAB or via the development of custom finite element analysis software but were not implemented in this thesis due to time constraints. Other improvements were also suggested for future work.

The thesis is to explore wireless location tracking algorithms based on geometric dilution of precision (GDOP) in the mobile environment. The GDOP can be used as an indication of positioning accuracy, affected by the geometric relationship between the target and sensing units. The smaller the GDOP is, the better positioning accuracy. By using the information of sensing units and time difference of arrival (TDOA) positioning method, we use extended Kalman filter as an estimator to track and predict the state of a moving target. From previous research, the lowest GDOP value, located at the center of a regular polygon, represents the best positioning accuracy in 2-D scenario with numerous sensing units. It is important to find the best locations for the sensing units. Simulated annealing algorithm was used in previous studies. However, it only finds a location at a time, and consumes computation load and time. Due to the above-mentioned reasons, we propose a location tracking system, which consists of a base traiver station and numerous mobile sensing units. By using the information of a base transceiver station and the predicted position of target, we can obtain the best locations for all the mobile sensing units with the calculation of rotation matrix. The locations can also be used as beacons for relocating mobile sensing units. It may take many cycles to move mobile sensing units to the best locations. We have to perform path planning for mobile sensing units. Due to the location change of the moving target, the routes need adjustment accordingly. If the predicted stay of a mobile sensing unit is inside the obstacle, we adjust the route of the mobile sensing unit to make it stay out of the obstacle. Therefore, we also propose a path planning scheme for mobile sensing units to avoid obstacles. Through simulations, the proposed method decreases the tracking time effectively, and find the best locations precisely. When mobile sensing units move toward the best locations, they successfully avoid obstacles and move toward the position with the minimum GDOP. Through the course, good positioning accuracy can be maintained.

In this thesis, a system to locate an electrostatic discharge (ESD) event within an electronic device has been developed. ESD can cause a device to fail legally required radiated emissions limits as well as disrupt intended operation. The system used a fast oscilloscope with four channels, each channel attached to a high frequency near-field antenna. These antennas were placed at known locations in three dimensional space to measure the fields radiated from the ESD event. A Time-Difference-of-Arrival technique was used to calculate the location of the ESD event. Quick determination of the ESD event location provides developers with a tool that saves them time and money by eliminating the time-consuming and tedious method of general ESD mitigation within a product.