This study proposes a new spectral representation called the Zeros of Z-Transform (ZZT), which is an all-zero representation of the z-transform of the signal. In addition, new chirp group delay processing techniques are developed for analysis of resonances of a signal. The combination of the ZZT representation with the chirp group delay processing algorithms provides a useful domain to study resonance characteristics of source and filter components of speech. Using the two representations, effective algorithms are developed for: source-tract decomposition of speech, glottal flow parameter estimation, formant tracking and feature extraction for speech recognition. The ZZT representation is mainly important for theoretical studies. Studying the ZZT of a signal is essential to be able to develop effective chirp group delay processing methods. Therefore, first the ZZT representation of the source-filter model of speech is studied for providing a theoretical background. We confirm through ZZT representation that anti-causality of the glottal flow signal introduces mixed-phase characteristics in speech signals. The ZZT of windowed speech signals is also studied since windowing cannot be avoided in practical signal processing algorithms and the effect of windowing on ZZT representation is drastic. We show that separate patterns exist in ZZT representations of windowed speech signals for the glottal flow and the vocal tract contributions. A decomposition method for source-tract separation is developed based on these patterns in ZZT. We define chirp group delay as group delay calculated on a circle other than the unit circle in z-plane. The need to compute group delay on a circle other than the unit circle comes from the fact that group delay spectra are often very noisy and cannot be easily processed for formant tracking purposes (the reasons are explained through ZZT representation). In this thesis, we propose methods to avoid such problems by modifying the ZZT of a signal and further computing the chirp group delay spectrum. New algorithms based on processing of the chirp group delay spectrum are developed for formant tracking and feature estimation for speech recognition. The proposed algorithms are compared to state-of-the-art techniques. Equivalent or higher efficiency is obtained for all proposed algorithms. The theoretical parts of the thesis further discuss a mixed-phase model for speech and phase processing problems in detail.

Globale Navigationssatellitensysteme (global navigation satellite systems, GNSS) ermöglichen die Positionsbestimmung, Navigation und Zeitübertragung überall auf der Erde und zu jeder Zeit. Dabei können durch spezielle Auswerteverfahren und die Berücksichtigung von Messabweichungen, denen die Beobachtungen der Satelliten unterliegen, deutlich höhere Genauigkeiten erreicht werden als ursprünglich vorgesehen. Ursachen für Messabweichungen sind neben Phänomenen, die den Signalweg beeinflussen, auch elektronische und elektromagnetische Effekte an den Satelliten und Empfangssystemen. Richtungsabhängige Verzögerungen der Codebeobachtungen (group delay variations, GDV) stellen eine solche Art der Messabweichung dar. Sie entstehen durch richtungsabhängige Sende- und Empfangseigenschaften der Satelliten- bzw. Empfangsantennen und sind frequenzabhängig. Aufgrund steigender Genauigkeitsanforderungen hat sich die Bestimmung und Korrektion von Messabweichungen zu einem wichtigen Forschungsfeld etabliert. Hier leistet die vorliegende Arbeit einen Beitrag. Sie beschäftigt sich mit der Bestimmung von GDV auf der Grundlage von Beobachtungen terrestrischer Referenzstationen, wobei die GDV der GNSS-Satellitenantennen im Vordergrund stehen. Da eine Codebeobachtung sowohl die GDV der Satellitenantenne als auch die der Empfangsantenne enthält, stellt die exakte Trennung beider Anteile eine besondere Herausforderung dar. Sie kann nur gelingen, wenn für eine der Antennen absolute Werte bekannt sind. Absolute GDV von Satelliten- und Empfangsantennen haben den Vorteil, dass sie unabhängig voneinander nutzbar sind. Im Gegensatz dazu beziehen sich relative Satellitenantennen-GDV auf die verwendeten Empfangsantennen und sind nicht unabhängig von ihnen. Die kumulative Dissertation basiert auf drei wissenschaftlichen Publikationen zur Bestimmung relativer und absoluter GDV. Am Beispiel relativer GDV der GPS-Satellitenantennen wird zunächst deren zeitliche Stabilität untersucht. Die Ergebnisse zeigen, dass von zeitlicher Stabilität über die Dauer von mindestens zwei Jahren ausgegangen werden kann. Daraufhin erfolgt mit Beobachtungen jeweils nur einer Orbitperiode die Bestimmung relativer GDV für die Satellitenantennen von GLONASS und Galileo. Es stellt sich heraus, dass Orbitperioden von mehreren Tagen die Datenakquise deutlich erleichtern. Zudem ermöglichen die Kriterien hinsichtlich des Equipments der ausgewählten Referenzstationen typspezifische Betrachtungen der Empfangsantennen. Schließlich können auf der Grundlage absoluter GDV-Korrektionen für GNSS-Empfangsantennen auch absolute GDV für die Satellitenantennen von GPS, GLONASS, Galileo, BeiDou und QZSS bestimmt werden. Mit diesem Ergebnis steht erstmals ein umfangreiches Set absoluter Multi-GNSS- und Multifrequenz-GDV für einen Großteil der GNSS-Satellitenantennen zur Verfügung. Es gewährt einen systemübergreifenden Überblick und kann zur Korrektion von Codebeobachtungen verwendet werden. Auch wenn sich die Genauigkeit der GDV-Schätzungen noch nicht abschließend beurteilen lässt, birgt die angewendete Methode das Potenzial, GDV mit einer Präzision von wenigen Zentimetern zu bestimmen.:Kurzfassung Abstract Inhaltsverzeichnis Abbildungsverzeichnis Tabellenverzeichnis Abkürzungsverzeichnis 1 Einleitung 1.1 Beschreibung richtungsabhängiger Codeverzögerungen 1.2 Stand der Forschung 1.3 Motivation 2 Bestimmung richtungsabhängiger Codeverzögerungen 2.1 Richtungen an Satelliten- und Empfangsantennen 2.2 Methoden 2.3 Code-Minus-Carrier-Methode 2.3.1 Code-Minus-Carrier-Linearkombination 2.3.2 Schätzung richtungsabhängiger Codeverzögerungen 2.3.3 Aspekte der untersuchten GNSS 2.4 Ergebnisse 3 Publikationen P1 Die zeitliche Stabilität der Code-Verzögerungen von GPS-Sendeantennen P2 Die Code-Verzögerungen von Galileo und GLONASS P3 Bestimmung absoluter Code-Verzögerungen für GNSS-Satellitenantennen auf der Grundlage absoluter Code-Verzögerungen von Empfangsantennen 4 Schlussfolgerungen und Ausblick Literaturverzeichnis Anhang / Global navigation satellite systems (GNSS) provide positioning, navigation, and timing services anywhere on Earth and at any time. Sophisticated processing methods and the consideration of measurement deviations make it possible to achieve much higher accuracies than originally intended. Measurement deviations originate, aside from phenomena affecting the signal path, from electronic and electromagnetic effects on the satellites and receiving systems. Direction-dependent delays of the code observations, so-called group delay variations (GDV), represent such a type of measurement deviations. They are caused by direction-dependent transmission and reception properties of the satellite and receiver antennas, respectively, and are frequency-dependent. Due to increasing accuracy requirements, the investigation and correction of GNSS measurement deviations has become an important field of research. This thesis makes a contribution to this field. It deals with the estimation of GDV based on GNSS observations of terrestrial reference stations, with a focus on the GDV occurring at the satellite antennas. Since GNSS code observations contain both the GDV of the satellite and that of the receiver antenna, the exact separation of both parts is a special challenge. It becomes possible only if absolute GDV are available for one of the antennas. Absolute GDV of satellite and receiver antennas have the advantage that they can be used independently of each other. On the contrary, relative satellite antenna GDV refer to the receiver antennas and are not independent from them. The cumulative dissertation is based on three scientific publications on the determination of relative and absolute GDV. First, the temporal stability of the satellite antenna GDV is investigated using the example of relative GDV for GPS satellite antennas. The results indicate that temporal stability can be assumed over a period of at least two years. Second, with observations of only one orbit period each, the determination of relative GDV for GLONASS and Galileo satellite antennas is carried out. It turns out that orbit periods of several days significantly facilitate data acquisition. In addition, the criteria regarding the equipment of the selected reference stations reveal type-specific properties of the receiver antennas. Finally, based on absolute GDV corrections for GNSS receiver antennas, absolute GDV can also be estimated for the satellite antennas of GPS, GLONASS, Galileo, BeiDou, and QZSS. With this result, a comprehensive set of absolute multi-GNSS and multi-frequency GDV is available for the majority of present GNSS satellite antennas for the first time. It provides a cross-system overview and can be used to correct code observations. Even if the accuracy of the GDV estimates cannot yet be conclusively assessed, the applied method has the potential to estimate GDV with a precision of a few centimeters.:Kurzfassung Abstract Inhaltsverzeichnis Abbildungsverzeichnis Tabellenverzeichnis Abkürzungsverzeichnis 1 Einleitung 1.1 Beschreibung richtungsabhängiger Codeverzögerungen 1.2 Stand der Forschung 1.3 Motivation 2 Bestimmung richtungsabhängiger Codeverzögerungen 2.1 Richtungen an Satelliten- und Empfangsantennen 2.2 Methoden 2.3 Code-Minus-Carrier-Methode 2.3.1 Code-Minus-Carrier-Linearkombination 2.3.2 Schätzung richtungsabhängiger Codeverzögerungen 2.3.3 Aspekte der untersuchten GNSS 2.4 Ergebnisse 3 Publikationen P1 Die zeitliche Stabilität der Code-Verzögerungen von GPS-Sendeantennen P2 Die Code-Verzögerungen von Galileo und GLONASS P3 Bestimmung absoluter Code-Verzögerungen für GNSS-Satellitenantennen auf der Grundlage absoluter Code-Verzögerungen von Empfangsantennen 4 Schlussfolgerungen und Ausblick Literaturverzeichnis Anhang

Although it has been well established that abnormal group delay is a real physical phenomenon and is not in violation of Einstein causality, there has been little investigation into whether or not such abnormal behaviour can be used to reduce signal latency in practical communication systems in the presence of noise. In this thesis, we use time-varying probability of error to determine if abnormal group delay “channels” can offer reduced signal latency. Since the detection system plays a critical role in the analysis, three important detection systems are considered: the correlation, matched filter and envelope detection systems. Our analysis shows that for both spatially negligible microelectronic systems and spatially extended microwave systems, negative group delay “channels” offer reduced signal latency as compared to conventional “channels”. The results presented in the thesis can be used to design a new generation of electronic and microwave interconnects with reduced or eliminated signal latency.

Although it has been well established that abnormal group delay is a real physical phenomenon and is not in violation of Einstein causality, there has been little investigation into whether or not such abnormal behaviour can be used to reduce signal latency in practical communication systems in the presence of noise. In this thesis, we use time-varying probability of error to determine if abnormal group delay “channels” can offer reduced signal latency. Since the detection system plays a critical role in the analysis, three important detection systems are considered: the correlation, matched filter and envelope detection systems. Our analysis shows that for both spatially negligible microelectronic systems and spatially extended microwave systems, negative group delay “channels” offer reduced signal latency as compared to conventional “channels”. The results presented in the thesis can be used to design a new generation of electronic and microwave interconnects with reduced or eliminated signal latency.

Abnormal electromagnetic wave propagation characterized by negative group velocity and consequently negative group delay (NGD) has been observed in certain materials as well as in artificially built structures. Within finite frequency intervals where an NGD phenomenon is observed, higher frequency components of the applied waveform are propagated with phase advancement, not delay, relative to the lower frequency components. These media have found use in many applications that require positive delay compensation and an engineered phase characteristic, such as eliminating phase variation with frequency in phase shifters, beam-squint minimization in phased array antenna systems, size reduction of feed-forward amplifiers and others. The three principal questions this thesis addresses are: can a generic formulation for artificial NGD structures based on electric circuit resonators be developed; is it possible to derive a quantitative functional relationship (asymptotic limit) between the maximum achievable NGD and the identified trade-off quantity (out-of-band gain); and, can a microwave circuit exhibiting a fully loss-compensated NGD propagation in both directions be designed and implemented? A generic frequency-domain formulation of artificial NGD structures based on electric circuit resonators is developed and characterized by three parameters, namely center frequency, bandwidth and the out-of-band gain. The developed formulation is validated through several topologies reported in the literature. The trade-off relationship between the achievable NGD on one hand, and the out-of-band gain on the other, is identified. The out-of-band gain is shown to be proportional to transient amplitudes when waveforms with defined “turn on/off” times are propagated through an NGD medium. An asymptotic limit for achievable NGD as a function of the out-of-band gain is derived for multi-stage resonator-based NGD circuits as well as for an optimally engineered linear causal NGD medium. Passive NGD media exhibit loss which can be compensated for via active elements. However, active elements are unilateral in nature and therefore do not allow propagation in both directions. A bilateral gain-compensated circuit is designed and implemented, which overcomes this problem by employing a dual-amplifier configuration while preserving the overall circuit stability.

Abnormal electromagnetic wave propagation characterized by negative group velocity and consequently negative group delay (NGD) has been observed in certain materials as well as in artificially built structures. Within finite frequency intervals where an NGD phenomenon is observed, higher frequency components of the applied waveform are propagated with phase advancement, not delay, relative to the lower frequency components. These media have found use in many applications that require positive delay compensation and an engineered phase characteristic, such as eliminating phase variation with frequency in phase shifters, beam-squint minimization in phased array antenna systems, size reduction of feed-forward amplifiers and others. The three principal questions this thesis addresses are: can a generic formulation for artificial NGD structures based on electric circuit resonators be developed; is it possible to derive a quantitative functional relationship (asymptotic limit) between the maximum achievable NGD and the identified trade-off quantity (out-of-band gain); and, can a microwave circuit exhibiting a fully loss-compensated NGD propagation in both directions be designed and implemented? A generic frequency-domain formulation of artificial NGD structures based on electric circuit resonators is developed and characterized by three parameters, namely center frequency, bandwidth and the out-of-band gain. The developed formulation is validated through several topologies reported in the literature. The trade-off relationship between the achievable NGD on one hand, and the out-of-band gain on the other, is identified. The out-of-band gain is shown to be proportional to transient amplitudes when waveforms with defined “turn on/off” times are propagated through an NGD medium. An asymptotic limit for achievable NGD as a function of the out-of-band gain is derived for multi-stage resonator-based NGD circuits as well as for an optimally engineered linear causal NGD medium. Passive NGD media exhibit loss which can be compensated for via active elements. However, active elements are unilateral in nature and therefore do not allow propagation in both directions. A bilateral gain-compensated circuit is designed and implemented, which overcomes this problem by employing a dual-amplifier configuration while preserving the overall circuit stability.

Penkiose disertacijos darbo dalyse nagrinėjamos asmens identifikavimo pagal pirštų atspaudus ir balsą problemos ir siūlomi jų sprendimai. Pirštų atspaudų požymių išskyrimo algoritmų kokybės įvertinimo problemą siūloma spręsti panaudojant sintezuotus pirštų atspaudus. Darbe siūlomos žinomo pirštų atpaudų sintezės algoritmo modifikacijos, kurios leidžia sukurti piršto atspaudo vaizdą su iš anksto nustatytomis charakteristikomis ir požymiais bei pagreitina sintezės procesą. Pirštų atspaudų požymių palyginimo problemos yra aptartos ir naujas palyginimo algoritmas yra siūlomas deformuotų pirštų palyginimui. Algoritmo kokybė yra įvertinta naudojant viešai prieinamas ir vidines duomenų bazes. Naujas asmens identifikavimo pagal balsą metodas remiantis tiesinės prognozės modelio grupinės delsos požymiais ir tų požymių palyginimo metrika kokybės prasme lenkia tradicinius asmens identifikavimo pagal balsą metodus. Pirštų ir balso įrašų nepriklausomumas yra irodytas ir asmens atpažinimas pagal balsą ir pirštų atspaudus kartu yra pasiūlytas siekiant išspręsti bendras biometrinių sistemų problemas. / This dissertation focuses on person identification problems and proposes solutions to overcome those problems. First part is about fingperprint feaures extraction algorithm performance evaluaiton. Modifications to a known synthesis algorithm are proposed to make it fast and suitable for performance evaluation. Matching of deformed fingerprints is discussed in the second part of the work. New fingerprint matching algorithm that uses local structures and does not perform fingerprint alignment is proposed to match deformed fingerprints. The use of group delay features of linear prediciton model for speaker identification is proposed in the third part of the work. New similarity metric that uses group delay features is described. It is demonstrated that automatic speaker identification system with proposed features and similarity metric outperforms traditional speaker identification systems. Multibiometrics using fingerprints and voice is adressed in the last part of the dissertation.

There is a growing demand for the high quality TV programs such as High Definition TV (HDTV). The CATV network is often a suitable solution to address this demand using a CATV modem delivering high data rate digital signals in a cost effective manner, thereby, utilizing a complex digital modulation scheme is inevitable. Exploiting complex modulation schemes, entails a more sophisticated modulator and distribution system with much tighter tolerances. However, there are always distortions introduced to the modulated signal in the modulator degrading signal quality.<p> In this research, the effect of distortions introduced by the RF band pass filter in the modulator will be considered which cause degradations on the quality of the output Quadrature Amplitude Modulated (QAM) signal. Since the RF filter's amplitude/group delay distortions are not symmetrical in the frequency domain, once translated into the base band they have a complex effect on the QAM signal. Using Matlab, the degradation effects of these distortions on the QAM signal such as Bit Error Rate (BER) is investigated.<p> In order to compensate for the effects of the RF filter distortions, two different methods are proposed. In the first method, a complex base band compensation filter is placed after the pulse shaping filter (SRRC). The coefficients of this complex filter are determined using an optimization algorithm developed during this research. The second approach, uses a pre-equalizer in the form of a Feed Forward FIR structure placed before the pulse shaping filter (SRRC). The coefficients of this pre-equalizer are determined using the equalization algorithm employed in a test receiver, with its tap weights generating the inverse response of the RF filter. The compensation of RF filter distortions in base band, in turn, improves the QAM signal parameters such as Modulation Error Ratio (MER). Finally, the MER of the modulated QAM signal before and after the base band compensation is compared between the two methods, showing a significant enhancement in the RF modulator performance.

There is a growing demand for the high quality TV programs such as High Definition TV (HDTV). The CATV network is often a suitable solution to address this demand using a CATV modem delivering high data rate digital signals in a cost effective manner, thereby, utilizing a complex digital modulation scheme is inevitable. Exploiting complex modulation schemes, entails a more sophisticated modulator and distribution system with much tighter tolerances. However, there are always distortions introduced to the modulated signal in the modulator degrading signal quality.<p> In this research, the effect of distortions introduced by the RF band pass filter in the modulator will be considered which cause degradations on the quality of the output Quadrature Amplitude Modulated (QAM) signal. Since the RF filter's amplitude/group delay distortions are not symmetrical in the frequency domain, once translated into the base band they have a complex effect on the QAM signal. Using Matlab, the degradation effects of these distortions on the QAM signal such as Bit Error Rate (BER) is investigated.<p> In order to compensate for the effects of the RF filter distortions, two different methods are proposed. In the first method, a complex base band compensation filter is placed after the pulse shaping filter (SRRC). The coefficients of this complex filter are determined using an optimization algorithm developed during this research. The second approach, uses a pre-equalizer in the form of a Feed Forward FIR structure placed before the pulse shaping filter (SRRC). The coefficients of this pre-equalizer are determined using the equalization algorithm employed in a test receiver, with its tap weights generating the inverse response of the RF filter. The compensation of RF filter distortions in base band, in turn, improves the QAM signal parameters such as Modulation Error Ratio (MER). Finally, the MER of the modulated QAM signal before and after the base band compensation is compared between the two methods, showing a significant enhancement in the RF modulator performance.

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