Multi-Elliptical Geometry of Scatterers in Modeling Propagation Effect at Receiver

In the proposed chapter, the authors present a geometric-statistical propagation model that defines three groups of received signal components, i.e., direct path, delayed scattering, and local scattering components. The multi-elliptical propagation model, which represents the geometry of scatterer locations, is the basis for determining the delayed components. For the generation of the local components, a statistical distribution is used. The basis for this model is a power angular spectrum (PAS) of the received signal, which is closely related to a type of propagation environment and transmitter-receiver spatial positions. Therefore, we have an opportunity to evaluate the influence of the environment type and an object motion direction on the basic characteristics such as envelope distribution, PAS, autocorrelation function, and spectral power density. The multi-elliptical model considers the propagation phenomena occurring in the azimuth plane. In the chapter, we will also show the 3D extension of modeling effects of propagation phenomena

A 3D spatial channel model for cellular radio

This thesis provides closed form expressions for the angular distribution in azimuth and elevation planes for a geometrically based single bounce spheroid model, The geometry of the spheroid is defined by the semi-major axis a and the semi-minor axis b. The other parameter of interest in the model is the distance D between the base station and the mobile station. The latter is assumed to be at the center of the spheroid. The mobile station is assumed to be the transmitter, while the base station is the receiver. This thesis investigates the effects of the above parameters on the angular distribution of the received waves. Important parameters such as the r.m.s angle spread in azimuth and elevation plane are calculated from the p.d.f. expressions derived. The behavior of these r.m.s angle spreads versus the ratio a/D or b/D respectively is also investigatedhttp://archive.org/details/adspatialchannel10945761

Channel characterisation and modelling for transcranial Doppler ultrasound.

The detection of micro-embolic signals (MES) is a mature application of transcranial Doppler (TCD) ultrasound. It involves the identification of abnormally highpitched signals within the arterial waveform as a method of diagnosis and prediction of embolic complications in stroke patients. More recently, algorithms have been developed to help characterise and classify MES using advanced signal processing techniques. These advances aim to improve our understanding of the causes of cereberovascular disease, helping to target the most appropriate interventions and quantifying the risk to patients of further stroke events. However, there are a number of limitations with current TCD systems which reduce their effectiveness. In particular, improvements in our understanding of the scattering effects in TCD ultrasound propagation channels will benefit our ability to develop algorithms that more robustly and reliably identify the consistency and material make-up of MES. This thesis explores TCD propagation channels in three related research areas. Firstly, a method of characterising TCD ultrasound propagation channels is proposed. Isotropic and non-isotropic three dimensional space (3-D) spherical scattering channel models are described in terms of theoretical reference models, simulation models, and sum of sinusoids (SoS) simulators, allowing the statistical properties to be analysed and reported. Secondly, a TCD ultrasound medical blood flow phantom is described. The phantom, designed to replicate blood flow in the middle cerebral arteries (MCA) for TCD ultrasound studies, is discussed in terms of material selection, physical construction and acoustic characteristics, including acoustic velocity, attenuation and backscatter coefficients. Finally, verification analysis is performed on the non-isotropic models against firstly, the blood flow phantom, and secondly, a patient recordings database. This analysis expands on areas of agreement and disagreement before assessing the usefulness of the models and describing their potential to improve signal processing approaches for detection of MES. The proposed non-isotropic channel reference model, simulation model, SoS simulator, and blood flow phantom are expected to contribute to improvements in the design, testing, and performance evaluation of future TCD ultrasound systems

Intelligence/Electronic Warfare (IEW) direction-finding and fix estimation analysis report. Volume 2: Trailblazer

An analysis of the direction finding (DF) and fix estimation algorithms in TRAILBLAZER is presented. The TRAILBLAZER software analyzed is old and not currently used in the field. However, the algorithms analyzed are used in other current IEW systems. The underlying algorithm assumptions (including unmodeled errors) are examined along with their appropriateness for TRAILBLAZER. Coding and documentation problems are then discussed. A detailed error budget is presented

Comparative studies of conceptual design and qualification procedures for a Mars probe/lander. Volume I - Summary Final report

System and subsystem design concepts for Mars probe/lander entry from interplanetary approach trajectory or orbit mission mode

RADAR Based Collision Avoidance for Unmanned Aircraft Systems

Unmanned Aircraft Systems (UAS) have become increasingly prevalent and will represent an increasing percentage of all aviation. These unmanned aircraft are available in a wide range of sizes and capabilities and can be used for a multitude of civilian and military applications. However, as the number of UAS increases so does the risk of mid-air collisions involving unmanned aircraft. This dissertation aims present one possible solution for addressing the mid-air collision problem in addition to increasing the levels of autonomy of UAS beyond waypoint navigation to include preemptive sensor-based collision avoidance. The presented research goes beyond the current state of the art by demonstrating the feasibility and providing an example of a scalable, self-contained, RADAR-based, collision avoidance system. The technology described herein can be made suitable for use on a miniature (Maximum Takeoff Weight \u3c 10kg) UAS platform. This is of paramount importance as the miniature UAS field has the lowest barriers to entry (acquisition and operating costs) and consequently represents the most rapidly increasing class of UAS

Identification of Technologies for Provision of Future Aeronautical Communications

This report describes the process, findings, and recommendations of the second of three phases of the Future Communications Study (FCS) technology investigation conducted by NASA Glenn Research Center and ITT Advanced Engineering & Sciences Division for the Federal Aviation Administration (FAA). The FCS is a collaborative research effort between the FAA and Eurocontrol to address frequency congestion and spectrum depletion for safety critical airground communications. The goal of the technology investigation is to identify technologies that can support the longterm aeronautical mobile communication operating concept. A derived set of evaluation criteria traceable to the operating concept document is presented. An adaptation of the analytical hierarchy process is described and recommended for selecting candidates for detailed evaluation. Evaluations of a subset of technologies brought forward from the prescreening process are provided. Five of those are identified as candidates with the highest potential for continental airspace solutions in L-band (P-34, W-CDMA, LDL, B-VHF, and E-TDMA). Additional technologies are identified as best performers in the unique environments of remote/oceanic airspace in the satellite bands (Inmarsat SBB and a custom satellite solution) and the airport flight domain in C-band (802.16e). Details of the evaluation criteria, channel models, and the technology evaluations are provided in appendixes

Polarimetric Radar Observations and Numerical Simulations of Tornadic Debris

Tornadic debris are critical aspects of tornado studies because airborne debris pose significant threats to life and property, and debris often dominate backscattered radar signals, causing biased Doppler velocity measurements. Polarimetric radar offers new research opportunities because debris produce a unique polarimetric radar signature called the tornadic debris signature (TDS). In this study, new applications of TDSs are examined using Transmission (T) matrix calculations, polarimetric radar observations, and numerical simulations. To illuminate electromagnetic scattering characteristics of different debris types, T-matrix calculations are presented. While most TDS studies have focused on tornado detection, this study conducts a detailed analysis of 14 TDS cases to determine relationships between TDS parameters and EF-rating. As tornado EF-rating increases, 90th percentile radar reflectivity factor, TDS height, and TDS volume increase, and 10th percentile co-polar cross-correlation coefficient and differential reflectivity decrease. While the TDS parameter analysis focuses on a single radar frequency, debris scattering characteristics vary depending on radar frequency, and thus multiple frequency polarimetric radar observations may provide new information about debris. In a statistical analysis of dual-wavelength TDSs, higher radar reflectivity factor and lower co-polar cross-correlation coefficient are observed at S band compared to C band, and negative differential reflectivity is sometimes observed simultaneously at both frequencies. Multiple frequency radar observations have additional utility in determining debris concentrations to assess debris loading impacts. To simulate polarimetric radar signatures, tornado vortices are simulated in a Large-Eddy Simulation (LES) model with a drag force coupling parameterization based on debris trajectories, enabling momentum exchange between air and debris. As debris loading increases, simulations reveal decreasing near-surface radial, tangential and vertical velocities in the lowest grid cell. Further increases in debris loading cause greater reductions in near-surface velocities and reduced tornado core tangential and vertical velocities. Using T-matrix calculations and LES model runs, equivalent radar reflectivity factor and two-way attenuation rates are calculated to determine if equivalent radar reflectivity factor or attenuation provide useful upper-bounds on debris loading. These simulations reveal that if sufficient amounts of debris loading are present to affect tornado dynamics, significant attenuation will occur at W band, in many cases fully attenuating the transmitted radar signal