International Telemetering Conference Proceedings / October 28-31, 1996 / Town and Country Hotel and Convention Center, San Diego, California / The tracking system is part of a telemetry ground station being developed for the UK Ministry of Defence. The design objective is a self-contained transportable system for field use in a vehicle or workshop environment, so that the system components are required to be man portable. Comprehensive facilities are required for the reception, display and analysis of telemetry data from a remote 1430-1450MHz airborne source at ranges of up to 205km. Since tracking over water is a prime requirement the system must accommodate severe multipath fading. A detailed analysis of the link budget indicates that there is a major conflict between cost, portability, antenna size and the receiver complexity required to achieve a satisfactory performance margin. A baseline system is analysed using a four foot antenna. Methods for improving the performance are then considered including polarisation, frequency and space diversity coupled with alternative antenna types and configurations. The optimum solution utilises two six foot diameter shaped beam single axis antennas of unique design in conjunction with a receiving system which economically combines the elements of polarisation, frequency and space diversity.

Dispersed spectrum cognitive radio systems represent a promising approach to exploit the utilization of spectral resources to full extent. Therefore, the performance analysis of such systems is conducted in this research. The Average symbol error probability of dispersed spectrum cognitive radio systems is derived for two cases: where each channel realization experiences independent and dependent Nakagami-m fading, respectively. In addition, the derivation is extended to include the effects of modulation type and order by considering M-PSK and M-QAM modulation schemes. We then study the impacts of topology on the effective transport capacity performance of ad hoc dispersed spectrum cognitive radio systems where the nodes assume 3- dimensional (3D) configurations. We derive the effective transport capacity considering a cubic grid distribution. In addition, numerical results are presented to demonstrate the effects of topology on the effective transport capacity of ad hoc dispersed cognitive radio systems.

The transmission rate and reliability are the most crucial elements of a communication system on sea platforms. In this thesis, the performance of a high speed and reliable communication system that can be used on ship to ship sea platforms will be evaluated. The two ray channel model is used in order to characterize the channel considering the refraction and reflection. Using the channel model, the path loss and the Shannon channel capacities are obtained for different systems. In order to increase the system performance, frequency diversity technique is used and a detailed comparison of diversity combining techniques is provided. As an alternative to Shannon channel capacity, cut off rate analysis is considered to get more realistic results about the rate of the communication system in that it takes modulation into account and the results are compared with the channel capacity. Block fading model and jamming effects on the achievable rate of the system is considered for different linear modulation techniques. Finally, an OFDM system design is given as an example using the tools obtained in this work.

In this thesis, target induced glint error phenomenon is analyzed and the glint reduction techniques are evaluated. Glint error reduction performance of the methods is given in a comparative manner. First, target glint is illustrated with the dumbbell model which has two point scatterers. This illustration of the glint error builds the basic notion of target scattering centers and effect of scattering characteristics on glint error. This simplest approach is also used to understand the glint reduction methods. In an effort to evaluate the glint reduction techniques, a model based upon the concept of coherent summation of scattering complexes is used . The model is also used for introducing the basic properties of glint phenomenon. Basics of the glint phenomenon and glint reduction techniques are discussed with particular emphasis on diversity methods. Frequency diversity and spatial diversity techniques are described and investigated with generated simulation data. The diversity selection methods which are used to eliminate the erroneous data are introduced and their performances are investigated. Glint error reduction results of various scenarios including both reduction techniques and selection methods are evaluated in comparison with each other. The results indicate that significant reduction of glint error is possible by the appropriate utilization of diversity techniques in radar systems.

The advent of Internet based digital services, and bandwidth-intensive business and personal applications has necessitated deployment of broadband network access technologies. Research analysts project that the U.S. market for broadband wireless networking will grow to nearly $2 billion by 2004 and Local Multipoint Distribution Services (LMDS) have enormous potential to emerge as the most reliable and cost-effective solution. However, in order to design and deploy LMDS systems, it is vital for system designers to be able to predict the behavior of mm-waves (28, 38 and 60GHz) during different weather conditions, especially rain. This research attempts to characterize the performance of pico-cell scenario broadband wireless channels by measuring path loss statistics during different weather conditions. Hardware and software components of a wideband direct-sequence spread spectrum (DSS) channel sounding system, used extensively throughout measurement campaigns, are discussed in detail in this dissertation. The measurement plan comprehensively describes the methodology, logistics, equipment setup, and calibration procedures for propagation measurement campaigns. Power Delay Profile (PDP) snapshots recorded during measurement campaigns are thoroughly analyzed using the 'Channel Imaging Analysis Suite' and Path Loss as well as Rain Attenuation statistics, calculated from recorded PDP data files, are classified and tabulated on the basis of measurement locations, propagation frequencies and antenna polarizations. Path Loss Exponent values are also calculated and Rain Attenuation statistics are compared with popular rain models. Results from Frequency Diversity measurement campaigns are also presented. / Master of Science

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La thèse a pour but de développer des algorithmes robustes de poursuite de phase multifréquence en environnement dégradé. L’objectif est d’élaborer de nouvelles structures pouvant opérer à des niveaux de rapport signal à bruit inférieurs aux limites des algorithmes actuellement implémentés dans des récepteurs grand public. Les problèmes de robustesse des algorithmes d’estimation de phase étant en grande partie causés par le phénomène de sauts de cycle, les différents axes de recherche se sont focalisés sur des nouvelles approches de développement de phase au sein des structures de poursuite. Pour ce faire, deux approches ont été étudiées et testées. Dans un premier temps, deux structures de poursuite monofréquence basées sur une DPLL conventionnelle ont été développées. Ces structures disposent d’un système externe de développement de phase visant à prédire et pré-compenser la sortie du discriminateur grâce à l’analyse des sorties du discriminateur ou des sorties du filtre de boucle. La réduction de la dynamique à estimer va alors permettre de réduire l’apparition des sauts de cycle se produisant au niveau du discriminateur. Par la suite, ce système de développement de phase a été adapté à la poursuite de phase multifréquence. Grâce à l’exploitation de la diversité en fréquence offerte par les signaux de navigation (i.e., de la proportionnalité des fréquences Doppler), il a été possible de mettre en place une étape de fusion de données qui a permis d’améliorer la précision de la prédiction de la sortie du discriminateur et donc d’améliorer la robustesse de la structure. Dans un second temps, les travaux de recherche se son taxés sur une nouvelle approche de poursuite de phase et de correction du phénomène de sauts de cycle basée sur une technique de filtrage Bayésien variationnel. Toujours en exploitant la diversité en fréquence des signaux de navigation, cette méthode suppose un modèle de dynamique de phase Markovien qui va imposer une certaine continuité de l’estimation et va permettre de fournir une estimation de phase développée. / This thesis aims at introducing multifrequency phase tracking algorithms operating in low C/N0environment. The objective is to develop new structures whose tracking limits are lower than thatof current algorithms used in mass market receivers. Phase tracking suffers from a lack of robustnessdue to the cycle slip phenomenon. Works have thus been focused on elaborating new phaseunwrapping systems. To do so, two different tracking approaches were studied. First, we have developed new monofrequency tracking loops based on a conventional DPLL. These structures aimat predicting the discriminator output by analyzing, thanks to a polynomial model, the last outputsamples of either the discriminator or the loop filter. Once the discriminator output is predicted,the estimated value is pre-compensated so that the phase dynamics to be tracked is reduced aswell as the cycle slip rate. Then, the unwrapping structure analyzing the loop filter outputs hasbeen extended to multifrequency signals. Using a data fusion step, the new multifrequency structuretakes advantage of the frequency diversity of a GNSS signal (i.e., proportionality of Dopplerfrequencies) to improve the tracking performances. Secondly, studies have been focused on developing a new multifrequency tracking algorithm using variational Bayesian filtering technique.This tracking method, which also uses the GNSS frequency diversity, assumes a Markovian phasedynamics that enforces the smoothness of the phase estimation and unwraps it.