Digital Filters and Signal Processing

Digital filters, together with signal processing, are being employed in the new technologies and information systems, and are implemented in different areas and applications. Digital filters and signal processing are used with no costs and they can be adapted to different cases with great flexibility and reliability. This book presents advanced developments in digital filters and signal process methods covering different cases studies. They present the main essence of the subject, with the principal approaches to the most recent mathematical models that are being employed worldwide

Analogue filter networks: developments in theory, design and analyses

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Generalized linear-in-parameter models : theory and audio signal processing applications

This thesis presents a mathematically oriented perspective to some basic concepts of digital signal processing. A general framework for the development of alternative signal and system representations is attained by defining a generalized linear-in-parameter model (GLM) configuration. The GLM provides a direct view into the origins of many familiar methods in signal processing, implying a variety of generalizations, and it serves as a natural introduction to rational orthonormal model structures. In particular, the conventional division between finite impulse response (FIR) and infinite impulse response (IIR) filtering methods is reconsidered. The latter part of the thesis consists of audio oriented case studies, including loudspeaker equalization, musical instrument body modeling, and room response modeling. The proposed collection of IIR filter design techniques is submitted to challenging modeling tasks. The most important practical contribution of this thesis is the introduction of a procedure for the optimization of rational orthonormal filter structures, called the BU-method. More generally, the BU-method and its variants, including the (complex) warped extension, the (C)WBU-method, can be consider as entirely new IIR filter design strategies.reviewe

Frequency-Agile Microwave Filters For Radars With Simultaneous Transmission and Reception

Multi-band/multi-mode wireless communication systems have been receiving increased attention recently due to their potential for spectrum management in a dynamic spectral environment. Similarly radar systems, which can operate in a variety of frequency bands, could provide significant flexibility in the operation for the future applications. However, multi-band/multi-mode operation adds to the complexity of the microwave systems. Reconfigurable RF/microwave components in general, and tunable filters in particular, have been shown to be promising in significantly reducing the system complexity. On the other hand, current trend of development in wireless communication and radar systems, forces more stringent requirements for electromagnetic spectrum sharing. Therefore, in many microwave applications a very high level of isolation between the channels are required. This is including simultaneous transmit-receive systems or co-site interference scenarios where the leakage from high power transmitter into receiver degrades the system performance. In these applications, conventional tunable bandpass/bandstop filters cannot provide enough isolation between transmitter and receiver. A promising solution which provides a tunable null, independent of the tunable transmission passband, is a dynamic-tunable bandpass-bandstop filter cascade. In this research, a frequency-agile bandpass-bandstop filter cascade for radar systems with simultaneous transmission and reception is designed to create advanced filtering functionality to isolate the desired signals from interfering signals in a spectrally-crowded environment. For a radar with simultaneous transmit and receive, two filter cascade will be required. Each filter will be used on a separate frequency agile transceiver but they will be synchronized to provide simultaneously a deep isolation region at one frequency for receive and a high power tolerant passband at an adjacent frequency for transmit

Optical and Microwave Beamforming for Phased Array Antennas

Phased array antenna has been used for a variety of military and civil applications, over the past five decades. Being structurally conformal and flexible, phased array antenna is highly suitable for mobile applications. Besides, it can form the agile or shaped beams required for interference cancellation or multifunction systems. Moreover, the spatial power combination property increases the effective radiated power of a transmitter phased array system. Similarly, in a receiver phased array, beamforming increases the signal to noise ratio by coherent integration of the desired signals. Despite its impressive potentials and properties, phased array antenna has not become a commercial product yet. Cost and complexity of phased array antenna are beyond the scales of consumer electronics devices. Furthermore, calibration is an essential requirement of such a complex system, which is a fairly time-consuming process and requires skilled man power. Moreover, the narrow bandwidth of microwave components degrades the broadband performance of phased array system. Finally, the majority of the beamforming algorithms developed so far have preconditions, which make them unsuitable for a low-cost system. The objective of this thesis is to provide a novel cost-effective solution to minimize the system complexity of the future intelligent antenna systems, without sacrificing the performance. This research demonstrates that a powerful, robust beamforming algorithm, integrated in an efficient single-receiver architecture, constitutes the essence of a low-cost phased array antenna. Thus, a novel beamforming technique, called Zero-knowledge algorithm is developed. It is investigated, both theoretically and experimentally, that the proposed algorithm can compensate for the hardware errors and imperfections of the low-cost components of the system. Zero-knowledge beamforming algorithm possesses significant properties. Neither a priori knowledge of the incoming signal direction, nor the exact characteristics of the phase control network are required in this method. Proper adjustment of the parameters, makes this algorithm appropriate for mobile systems, particularly those installed on vehicles. The algorithm alleviates the drawbacks of analog phase shifters, such as imbalanced insertion loss and fabrication tolerances. Furthermore, this algorithm can serve as the core of a direction-of-arrival estimation technique, which senses the minor deflections of the array heading. For broadband applications optical delay lines must be used in the phase control network of the phased array systems, which are costly. Nevertheless, employing miniaturized delay lines can significantly reduce the device area, and consequently, the fabrication cost. Thus, in this research four types of miniaturized optical delay lines, designed in slow-wave structures, are analyzed, which can provide a large delay per length. In addition, two novel optical beamforming techniques, based upon the properties of Zero-knowledge algorithm, are developed for transmitter and receiver phased arrays

Zweifrequenz Magnetic-Particle-Imaging-Scanner - Hardware für mobilityMPI

Magnetic Particle Imaging (MPI) ist eine neue tomographische Bildgebungsmethode, welche magnetische Nanopartikel als Marker nutzt und potentielle Anwendungsmöglichkeiten in der Medizin und medizinischen Forschung bietet. Durch seine Auflösung im mm-Bereich und seine hohe zeitliche Auflösung ist es für viele Anwendungen geeignet. Da MPI ohne ionisierende Strahlung arbeitet, bietet eine Substitution von radiologischen Untersuchungen Vorteile für Patient und medizinisches Personal. Eine Herausforderung ist die Entwicklung von Anwendungsmöglichkeiten, die über die Fähigkeiten der etablierten Methoden hinausgehen. Ein möglicher Vorteil von MPI ist die Nutzung von Nanopartikeln, welche z.B. durch Funktionalisierung der Oberfläche kontrolliert mit ihrer Umgebung interagieren können. Durch das Ausnutzen der Partikeldynamik können diese Interaktionen magnetisch mit MPI gemessen und eine räumliche Darstellung des Partikelzustands gewonnen werden. Die vorliegende Arbeit beschreibt die Entwicklung und Anwendung eines MPI-Scanners, welcher speziell für die Demonstration und Erforschung der funktionalen Bildgebungsmöglichkeiten mit MPI unter Ausnutzung der Mobilitätsinformation der Partikel entworfen wurde. Dieses Konzept, welches als mobility-MPI (mMPI) bezeichnet wird, kann durch verschiedene Verfahren unter Ausnutzung der Brownschen Relaxation realisiert werden. Ein Verfahren ist die Verwendung zweier Anregungsfrequenzen, was die Separation der Partikeldynamik von der räumlichen Verteilung ermöglicht. Da aktuelle MPI Scanner Sende- und Empfangsschaltungen besitzen, welche an die Anregungsfrequenz angepasst sind, erfordert das Mehrfrequenz-mMPI Hardwareerweiterungen gegenüber konventionellen Scannern. Die vorliegende Arbeit beschreibt detailliert das Design und die Konstruktion eines Magnetic Particle Spectrometers und eines mMPI-Systems und ihrer Komponenten. Mehrere Entwurfsverfahren, wie z.B. eine Methode zur präzisen Vorhersage der parasitären Effekte bei Spulen, wurden im Zuge des Design-Prozesses entwickelt. Erwähnenswert ist ebenfalls das Design der Sende- und Empfangsfilter, welche hohe Dämpfungswerte im Sperrbereich bei guter Linearität liefern. Die Entwicklung einer volldifferentiellen Empfangsspule ist ein weiterer interessanter Aspekt. Der neue Scanner wurde ausgehend von konventionellen ein- und zweidimensionalen MPI-Bildern genutzt, um die Eignung von MPI für die räumlich aufgelöste funktionale Bildgebung mittels Partikeldynamik zu zeigen.Magnetic Particle Imaging (MPI), being a new tomographic imaging modality based on magnetic nanoparticle tracers, offers potential applications in medicine and medical research. Possessing spatial resolution in the millimeter range and high temporal resolution, it is well suited for many applications. Since MPI doesn't rely on ionizing radiation, substitution of radiological methods by MPI benefits the safety of patients and medical staff. One of the challenges MPI faces is to provide capabilities that surpass what is currently possible with tracer based imaging systems. A possible advantage of MPI is the presence of nanoparticle tracers that can be modified to interact in well defined ways with their environment through surface functionalization. By exploiting particle dynamics, these interactions can be measured magnetically and can provide a spatially resolved map of particles states, enabling quantitative, functional imaging. This work describes the development and application of a MPI scanner designed specifically to demonstrate and further research the functional imaging capability of MPI through the measurement of particle mobility. This concept, called moblity MPI (mMPI), can be realized based on the Brownian relaxation mechanism. One possible technique involves the use of multiple excitation frequencies, that can be used to separate information on the spatial distribution from particle dynamics. Since the particle relaxation is inherently dependent on the excitation frequency, acquiring the same image at several drive frequencies provides the additional data required for functionally and spatially resolved MPI. Since current MPI scanners rely on transmit and receive chains tuned to the excitation frequency, the scanner hardware needs to be adapted. This thesis describes in detail the design and construction of a MPS and a mMPI system and their components. Several design techniques, such as a method for the accurate prediction of coil parasitics, have been developed for this task. Other noteworthy aspects are the design of transmit and receive filters, offering high stop band attenuation and good linearity. The development of a fully differential receive coil completes the effort to provide a system suitable for the demonstration of mMPI. After acquiring conventional one- and two-dimensional MPI images, the new scanner was used to demonstrate the capability of MPI to provide spatially resolved information on particle mobility

Multi-dimensional lattice equaliser for Q2 PSK

The aim of this dissertation was the design, implementation and performance evaluation of a Recursive Least Squares (RLS), lattice based, adaptive, multidimensional, decision feedback equaliser (DFE) for the spectrally efficient four-dimensional digital modulation technique, re¬ferred to as Quadrature-Quadrature Phase-Shift Keying, Q2pSK. Q2PSK constitutes a relatively new modulation technique, and the application of adaptive equalisation to this technique has not yet been considered in the open literature. This dissertation represents an in depth study into the Q2PSK modulation technique, as well as the optimal implementation, in simulation, of such a modem to aid the inclusion of the adap¬tive lattice DFE, for application to high speed mobile digital communication over the V /UHF channel in the presence of multi path propagation. Specific aspects of synchronization applicable to this modem platform are also addressed. An in depth study was also conducted into the realisation of a V /UHF channel simulation, capable of producing a Ricean and/or Rayleigh fad¬ing multipath propagation environment for the evaluation of the modem platform and adaptive equaliser structure. The theoretical analysis of the effect of multi path on a Q2PSK signal led to the correct design of the adaptive lattice structure, as well as the correct interfacing of the equaliser to the receiver platform. The performance of the proposed synchronisation strategies, in tandem with the equalisation technique were evaluated for several static, as well as fading multipath channels. The simulation results obtained show the equaliser operates correctly, and can give large performance gains over the static matched filter (matched to the transmitted waveform) implementation of the modem platform. Several simulations were specifically designed to highlight the performance limitations of the adaptive equalisation technique.Dissertation (MEng (Digital Communication))--University of Pretoria, 2006.Electrical, Electronic and Computer Engineeringunrestricte