Dissertations / Theses on the topic 'Mismatched Filter'

En raison de la croissance continue des applications électromagnétiques, le spectre devient de plus en plus encombré. Une solution possible à ce problème consiste à créer des systèmes radar-communication joints qui utilisent la même bande passante pour réaliser les deux applications. Dans cette thèse, nous nous intéressons à un système exploitant une forme d'onde issue du monde des communications pour réaliser conjointement de l'imagerie radar et un transfert d'information. Pour cela, parmi la multitude de codes existants, nous avons choisi d'utiliser des codes modulés continument en phase CPM, et plus particulièrement une sous-famille appelée Continuous Phase Frequency Shift-Keying codes. Les propriétés de ceux-ci, notamment en ce qui concerne l'occupation spectrale, sont d'abord étudiées et comparées à d'autres codes représentatifs des communications. Cependant, ces formes d'ondes présentent des qualités de compression dégradées par rapport au chirp habituellement utilisé en radar. En particulier les lobes secondaires résultant de la compression avec le filtre adapté sont plus élevés, nuisant à la qualité de l'image SAR résultante. Un filtre désadapté qui minimise l'énergie des lobes secondaires est proposé, ainsi qu'un algorithme rapide qui fournit les filtres pour tous les signaux émis en un temps de calcul raisonnable. Ce filtre désadapté est amélioré pour pouvoir traiter des valeurs inconnues de décalage Doppler ou de retard hors grille qui peuvent s'appliquer sur le signal reçu. De tels problèmes peuvent être généralisés à d'autres applications radar que le SAR. Une fois le choix de la méthode de compression d'impulsion établi, une évaluation des résultats est proposée. D'une part, des images SAR re-synthétisées sont générées, reconstruites à partir de données réelles basées sur le chirp, en utilisant des codes modulés continument et des filtres désadaptés, et différents outils de comparaison sont utilisés pour s'assurer de leurs performances. D'autre part, des données réelles sont acquises dans un cadre ISAR, afin de valider notre système dans un contexte réaliste. Finalement, nous pouvons apporter une réponse positive à la question suivante : pouvons-nous créer un système conjoint SAR-communication qui transmet des informations et fournit des images radar de haute qualité ?
Due to the continuous growth of electromagnetic applications, the spectrum gets more and more congested. A possible solution to this problem is the creation of joint radar-communication systems, because they can alleviate the spectrum occupancy by using the same bandwidth to perform both applications. In this thesis, a joint Synthetic Aperture Radar (SAR)-Communication system based on a communication waveform is considered. To do so, among all the existing codes, we chose Continuous Phase Modulated codes (CPM), and more specifically a sub-family called Phase Frequency Shift-Keying codes (CPFSK). Their properties, in particular the spectral occupation, are first studied and compared to other well-known communication codes. However, these waveforms present degraded compression qualities when compared to the usual chirp used for radars. More specifically, the sidelobes generated from the Matched Filter compression are higher, and thus deteriorate the resulting SAR image. The mismatched filter that minimizes the sidelobe level is proposed along with a fast algorithm that provides the filters for all the transmitted signals during an acceptable computational cost. This mismatched filter is further improved so that it can deal with unknown parameters. More precisely, if unknown Doppler shift or off-grid delay values are applied to the received signal, then an improved mismatched filter is provided. Such a problem can be extended to other radar applications. Once the range compression method choice is established, an evaluation of the results is proposed. On the one hand, re-synthesized SAR images are generated, reconstructed from real chirp-based data, using CPM codes and mismatched filters, and different comparison tools to ensure their performance.On the other hand, real data are acquired in an ISAR framework, in order to validate our system in a realistic context. Finally, we can provide a positive answer to the question: can we create a joint SAR-communication system that transmits information and provides an image of good radar quality?

The research presented in this dissertation is on the development of advanced reduced rank adaptive signal processing for airborne radar space-time adaptive processing (STAP) and steering vector mismatch robustness. This is an important area of research in the field of airborne radar signal processing since practical STAP algorithms should be robust against various kinds of mismatch errors. The clutter return in an airborne radar has widely spread Doppler frequencies; therefore STAP, a two-dimensional adaptive filtering algorithm is required for effective clutter and jamming cancellation. Real-world effects in nonhomogeneous environments increase the number of adaptive degrees of freedom required to adequately suppress interference. The increasing computational complexity and the need to estimate the interference from a limited sample support make full rank STAP impractical. The research presented here shows that the reduced rank multistage Wiener filter (MWF) provides significant subspace compression better than any previous techniques in a nonhomogeneous environment. In addition, the impact of steering vector mismatch will also be examined on the MWF. In an airborne radar environment, it is well known that calibration errors and steering vector mismatch can seriously degrade adaptive array performance and result in signal cancellation. These errors can be caused by many non-ideal factors such as beam steering angle errors, multipath propagation, and phase errors due to array imperfections. Since the MWF centrally features the steering vector on its formulation, it is important to assess the impact of steering vector mismatch. In this dissertation, several novel techniques for increasing robustness are examined and applied to the MWF. These include derivative constraints, quiescent pattern control (QPC) techniques, and covariance matrix tapers (CMT). This research illustrates that a combination of CMT and QPC, denoted CMTQ, is very effective at mitigating the impact of steering vector mismatch. Use of CMTQ augmentation provides the steering vector mismatch robustness that we desire while improving the reduced-rank and reduced sample characteristics of the MWF. Results using Monte Carlo simulations and experimental Multichannel Airborne Radar Measurements (MCARM) data confirm that the use of CMTQ gives superior performance to steering vector errors at a much reduced rank and sample support as compared to conventional techniques.
Ph. D.

In radars, matched filters are used in the receiver of the system. Since the target velocity is not known a priori, degradation occurs due to mismatch of the return signal and the matched filter. The performance of the radar can be improved by using a bank of matched filters. The first topic investigated in this work is optimization of the bank of matched filter structure. Two methods are proposed for the design of the parallel filter structure and computations are performed with both methods. The output signal of a radar receiver filter consists not only of the main peak from the target but also of range sidelobes. In a multi-target radar environment, the sidelobes of one large target may appear as a smaller target at another range, or the integrated sidelobes from targets or clutter may mask all the information of another target. The second part of this thesis discusses the methods for decreasing the sidelobe level of the receiver output. Two methods are studied for this purpose. The first is the classical amplitude weighting and the second is the use of an inverse filter that minimizes total sidelobe energy. Both methods decrease the sidelobe levels while bringing a mismatch loss and main peak broadening. For the inverse filter case it is observed that the effect of inverse filter becomes evident as the filter length is increased beyond some point. Finally, the effects of quantization on video signal and the receiver filter coefficients are evaluated. It is observed that 16 bits quantization is sufficient for all kinds of receiver filters tested.

This work describes a framework for simultaneous estimation and modeling (SEAM) of dynamic systems using non-Gaussian belief fusion by first presenting the relevant fundamental formulations, then building upon these formulations incrementally towards a more general and ubiquitous framework. Multi-Gaussian belief fusion (MBF) is introduced as a natural and effective method of fusing non-Gaussian probability distribution functions (PDFs) in arbitrary dimensions efficiently and with no loss of accuracy. Construction of some multi-Gaussian structures for potential use in MBF is addressed. Furthermore, recursive Bayesian estimation (RBE) is developed for linearized systems with uncertainty in model parameters, and a rudimentary motion model correction stage is introduced. A subsequent improvement to motion model correction for arbitrarily non-Gaussian belief is developed, followed by application to observation models. Finally, SEAM is generalized to fully nonlinear and non-Gaussian systems. Several parametric studies were performed on simulated experiments in order to assess the various dependencies of the SEAM framework and validate its effectiveness in both estimation and modeling. The results of these studies show that SEAM is capable of improving estimation when uncertainty is present in motion and observation models as compared to existing methods. Furthermore, uncertainty in model parameters is consistently reduced as these parameters are updated throughout the estimation process. SEAM and its constituents have potential uses in robotics, target tracking and localization, state estimation, and more.
Doctor of Philosophy
The simultaneous estimation and modeling (SEAM) framework and its constituents described in this dissertation aim to improve estimation of signals where significant uncertainty would normally introduce error. Such signals could be electrical (e.g. voltages, currents, etc.), mechanical (e.g. accelerations, forces, etc.), or the like. Estimation is accomplished by addressing the problem probabilistically through information fusion. The proposed techniques not only improve state estimation, but also effectively "learn" about the system of interest in order to further refine estimation. Potential uses of such methods could be found in search-and-rescue robotics, robust control algorithms, and the like. The proposed framework is well-suited for any context where traditional estimation methods have difficulty handling heightened uncertainty.

Nonuniform sampling occurs in many practical applications either intentionally or unintentionally. This thesis deals with the reconstruction of two-periodic nonuniform signals which is of great importance in two-channel time-interleaved analog-to-digital converters. In a two-channel time-interleaved ADC, aperture delay mismatch between the channels gives rise to a two-periodic nonuniform sampling pattern, resulting in distortion and severely affecting the linearity of the converter. The problem is solved by digitally recovering a uniformly sampled sequence from a two-periodic nonuniformly sampled set. For this purpose, a time-varying FIR filter is employed. If the sampling pattern is known and fixed, this filter can be designed in an optimal way using least-squares or minimax design. When the sampling pattern changes now and then as during the normal operation of time-interleaved ADC, these filters have to be redesigned. This has implications on the implementation cost as general on-line design is cumbersome. To overcome this problem, a novel time-varying FIR filter with polynomial impulse response is developed and characterized in this thesis. The main advantage with these filters is that on-line design is no longer needed. It now suffices to perform only one design before implementation and in the implementation it is enough to adjust only one variable parameter when the sampling pattern changes. Thus the high implementation cost is decreased substantially.

Filter design and the associated performance metrics have been validated using MATLAB. The design space has been explored to limits imposed by machine precision on matrix inversions. Studies related to finite wordlength effects in practical filter realisations have also been carried out. These formulations can also be extended to the general M - periodic nonuniform sampling case.

The growth in the number of wireless devices and applications underscores the need for characterizing and mitigating interference induced problems such as distortion and blocking. A typical interference scenario involves the detection of a small amplitude signal of interest (SOI) in the presence of a large amplitude interfering signal; it is desirable to attenuate the interfering signal while preserving the integrity of SOI and an appropriate dynamic range. If the frequency of the interfering signal varies or is unknown, an adaptive notch function must be applied in order to maintain adequate attenuation. This work explores the performance space of a phase cancellation technique used in implementing the desired notch function for communication systems in the 1-3 GHz frequency range. A system level model constructed with MATLAB and related simulation results assist in building the theoretical foundation for setting performance bounds on the implemented solution and deriving hardware specifications for the RF notch subsystem devices. Simulations and measurements are presented for a Low Noise Amplifer (LNA), voltage variable attenuators, bandpass filters and phase shifters. Ultimately, full system tests provide a measure of merit for this work as well as invaluable lessons learned. The emphasis of this project is the on-wafer LNA measurements, dependence of IC system performance on mismatches and overall system performance tests. Where possible, predictions are plotted alongside measured data. The reasonable match between the two validates system and component models and more than compensates for the painstaking modeling efforts. Most importantly, using the signal to interferer ratio (SIR) as a figure of merit, experimental results demonstrate up to 58 dB of SIR improvement. This number represents a remarkable advancement in interference rejection at RF or microwave frequencies.

Thesis (Ph.D.)--State University of New York at Buffalo, 2007.
Title from PDF title page (viewed on Feb. 13, 2009) Available through UMI ProQuest Digital Dissertations. Thesis adviser: Fam, Adly T. Includes bibliographical references.

碩士
國立交通大學
機械工程學系
100
In the last few years, Run-to-Run (RtR) control techniques have been developed and used to semiconductor manufacturing processes to maintain process targets and improve the yield of products. Among the RtR controllers, Exponentially Weighted Moving Average (EWMA), double-EWMA and Predicted Correct Control (PCC) are useful methods for online RtR estimation. However, incorrect selection of the RtR control parameters can have the opposite effect on the controlled process output. Conventional RtR controllers may fail in satisfying performance requirement especially when the system has model mismatch and the environmental perturbation. First, this thesis has discuss and analysis performance of EWMA controller and combine Kalman Filter in run-to-run control to deal with known disturbance : DT、RWD、IMA(1,1)、ARMA(1,1)、ARIMA(1,1,1). Then, a dynamic-tuning control structure having the capability of adjusting the system parameters dynamically that used to unknown disturbance is proposed in this thesis. There are two schemes in this control structure: a model mismatch self-tuning module and Kalman Filter used to estimate disturbance. The control structure, termed Self-Tuning model mismatch Kalman Filter controller (STKF), can reject process disturbance, reduce model mismatch and achieve expected performance.

Delta-sigma modulators are currently a very popular technique for making high-resolution analog-to-digital and digital-to-analog converters. These oversampled data converters have several advantages over conventional Nyquist-rate converters, including an insensitivity to many analog component imperfections, a simpler antialiasing filter and reduced accuracy requirements in the sample and hold. Though the initial uses of delta-sigma modulators were in the audio field, the development of bandpass modulators opened up the application range to radar systems, digital communication systems and instruments which convert IF, or even RF, analog signals directly to digital form. This thesis presents a method used to analyze and synthesize continuous-time delta-sigma modulators for given specifications. A fourth-order prototype continuous-time bandpass delta-sigma modulator employing g[subscript m]-LC resonator structure is demonstrated on a PCB board and measurement results corroborate the theory. To allow the construction of very high performance delta-sigma modulators, this thesis presents an architecture for a multibit DAC constructed from unit elements which shapes element mismatches. Theoretical analysis and simulation shows that this architecture greatly increases the noise attenuation in the band-of-interest and facilitates the use of multibit quantization in delta-sigma modulators. The methods presented in this thesis will allow high-frequency wideband bandpass delta-sigma modulators to be constructed.
Graduation date: 1996

碩士
國立交通大學
電機資訊國際學程
108
In digital wireless communication, the performance of the system is measured by two important measurement values which are Error Vector Magnitude (EVM) for the transmitter and Bit Error Rate (BER) for the receiver. Pulse Shaping Filter (PSF) is one of the essential components in the digital communication system due to its benefit of reducing bandwidth frequency of the transmitted signal and eliminating Inter-Symbol Interference (ISI). However, because of the limited number of coefficients that can be implemented in the real circuit, PSF usually introduces non-ideal effects that degrade both EVM and BER of the system. The two other non-ideal effects which affect the performance of the system is IQ mismatch and DC voltage offset. These two effects are usually introduced by low-cost RF analog circuit in the communication system and have a large influence to the system performance. Therefore, estimation and compensation of IQ mismatch and DC voltage offset are an extremely important task for the design of any communication system. This thesis proposes a designed of PSF and IQ mismatch and DC voltage offset calibration module which is able to meet transmitter EVM requirement stated by IEEE 802.11ad standard and receiver BER requirement of less than 3 error bits per every one thousands of sent bits under condition of using 16 QAM modulation scheme and Signal to Noise ratio (SNR) of 17dB. The hardware of PSF and IQ mismatch and DC voltage offset calibration module are designed for 4X parallelism data processing and are able to work at the 625MHz operating clock. The design of these two modules allows the overall system can archive the symbol rate of the 2.5GHz and a physical data rate of 10Gbps when 16 QAM modulation is used. We try to reduce the area and power of design by choosing the optimized word-length based on the simulation result. The design is synthesized using 28nm HPC+ technology provided by TSMC to generate gate-level netlist. The function of design is verified by running gate-level simulation. For a complicate wireless communication chip, function testing is extremely important before the tape-out stage due to the high cost of the chip manufacturing process. Function testing of design would help reduce the possibilities of failed function after the chip is made. In this thesis, we would like to introduce a testing procedure for the transmitter side of our baseband processor using equipment from National Instrument (NI). By doing this, we are able not only to verify again the function of baseband design but also to prove that our design can successfully work with other components of the communication system, for example, DAC/ADC and RF circuit.

We consider two transceivers equipped with multiple antennas that intend to communicate i.e. both of which transmit and receive data in a TDD fashion. Assuming that the responses of the physical communication channels between these two nodes are linear and reciprocal (time invariant or with very slow time variations), and by exploiting the closed loop conversation between these nodes, we have proposed efficient algorithms allowing to adaptively identify the Best Singular Mode (BSM) of the channel (those algorithms are for training, blind, and semi-blind channel identification). Unlike other proposed algorithms, our proposed adaptive algorithms are robust to noise as the involved step-size allows a trade-off to reduce the impact of the additive noise at the expense of some estimation delay. In practice, however, the reciprocity of the equivalent channels is lost because of the mismatch between the transmit and the receive filters of the communicating nodes. This mismatch causes significant degradation in the performance of the BSM estimation. Therefore, we have also proposed adaptive self-calibrating algorithms (which do not require any additional RF circuitry) that account for such a mismatch. In addition, we have conducted a convergence analysis of the BSM algorithm and extended it to estimate multiple modes simultaneously. Finally, we have also proposed an adaptive, iterative algorithm that is capable of allocating power in such a way that maximizes the capacity of a SISO OFDM communication system.
Thesis (Ph.D, Electrical & Computer Engineering) -- Queen's University, 2010-07-21 16:53:33.077

Run-of-mine ore milling circuits are generally difficult to control owing to the presence of strong external disturbances, poor process models and the unavailability of important process variable measurements. These shortcomings are common for processes in the mineral-processing industry. For processes that fall into this class, the peripheral control tools in the control loop are considered to be as important as the controller itself. This work addresses the implementation of peripheral control tools on a run-of-mine ore milling circuit to help overcome the deteriorated control performance resulting from the aforementioned shortcomings. The effects of strong external disturbances are suppressed through the application of a disturbance observer. A fractional order disturbance observer is also implemented and a novel Bode ideal cutoff disturbance observer is introduced. The issue of poor process models is addressed through the detection of significant mismatch between the actual plant and the available model from process data. A closed-form expression is given for the case where the controller has a transfer function. If the controller does not have a transfer function, a partial correlation analysis is used to detect the transfer function elements in the model transfer function matrix that contain significant mismatch. The mill states and important mill parameters are estimated with the use of particle filters. Simultaneous state and parameter estimation is compared with a novel dual particle filtering scheme. A sensitivity analysis shows the class of systems for which dual estimation would provide superiorestimation accuracy over simultaneous estimation. The implemented peripheral control tools show promise for current milling circuits where proportional-integral-derivative (PID) control is prevalent, and also for advanced control strategies, such as model predictive control, which are expected to become more common in the future. AFRIKAANS : Maalkringe wat onbehandelde erts maal is oor die algemeen moeilik om te beheer as gevolg van die teenwoordigheid van sterk eksterne steurings, onakkurate aanlegmodelle en metings van belangrike prosesveranderlikes wat ontbreek. Hierdie probleme is algemeen vir aanlegte in die mineraalprosesseringsbedryf. Vir aanlegte in hierdie klas word die randbeheerinstrumente as net so belangrik as die beheerder beskou. Hierdie verhandeling beskryf die implementering van randbeheerinstrumente vir ’n maalkring wat onbehandelde erts maal, om die verswakte beheerverrigting teen te werk wat veroorsaak word deur bogenoemde probleme. Die impak van sterk eksterne steurings word teengewerk deur die implementering van ’n steuringsafskatter. ’n Breuk-orde-steuringsafskatter is ook geïmplementeer en ’n nuwe Bode ideale afsnysteuringsafskatter word voorgestel. Die kwessie van onakkurate aanlegmodelle word hanteer deur van die aanlegdata af vas te stel of daar ’n verskil is tussen die aanleg en die beskikbare model van die aanleg. ’n Uitdrukking word gegee vir hierdie verskil vir die geval waar die beheerder met ’n oordragsfunksie voorgestel kan word. Indien die beheerder nie ’n oordragsfunksie het nie, word van ‘n parsiële korrelasie-analise gebruik gemaak om die element, of elemente, in die aanleg se oordragsfunksiematriks te identifiseer wat van die werklike aanleg verskil. Die toestande en belangrike parameters in die meul word beraam deur van partikel-filters gebruikte maak. Gelyktydige toestand- en parameter-beraming word vergelyk met ’n nuwe dubbel-partikelfilter skema. ’n Sensitiwiteitsanalise wys die klas van stelsels waarvoor dubbel-afskatting meer akkurate waardes sal gee as gelyktydige afskatting. Die voorgestelde randbeheerinstrumente is toepaslik vir huidige maalkringe waar PID-beheer algemeen is, asook vir gevorderde beheerstrategieë, soos model-voorspellende beheer, wat na verwagting in die toekoms meer algemeen sal word. Copyright
Dissertation (MEng)--University of Pretoria, 2012.
Electrical, Electronic and Computer Engineering
unrestricted

The functionality provided by mobile devices such as cellular phones and tablets continues to increase over the years, with integration of an ever larger number of wireless standards within a given device. In several of these designs, each standard supported by a device requires its own IC receiver to be mounted on the device’s PCB. In multistandard and multimode radios, it is desirable to integrate all receivers onto the same IC as the digital processors for the standards, in order to reduce device cost and size. Ideally all the receivers should also share a single signal chain. Since each standard has its own requirements for linearity and noise figure, and each standard operates at a different RF carrier frequency, implementing such a receiver is very challenging. Such a receiver could be theoretically implemented using a broadband mixing receiver or by direct sampling by a high-speed analog-to-digital converter (ADC). Broadband mixing requires the use of a harmonic rejection mixer (HRM) or tunable band pass filter to remove harmonic mixing effects, which in the past have suffered from a large primary clock tuning range and high power consumption. However, direct sampling of the RF input requires a high-speed ADC with large dynamic range which is typically limited by clock timing skew, clock jitter, or harmonic folding. In this dissertation, techniques for programmable broadband radio receivers are proposed. A local oscillator (LO) synthesis method within HRMs is proposed which reduces the required primary clock tuning range in broadband receivers. The LO synthesis method is implemented in 130-nm CMOS. A clocking technique is introduced within the two-stage HRM, which helps in achieving state-of-the-art harmonic rejection performance without calibration or harmonic filtering. An analog frequency synthesis based broadband channelizer is proposed using the LO synthesis method which is capable of channelizing a broadband input using a single mixing stage and primary clock frequency. A frequency-folded ADC architecture is proposed which enables high-speed sampling with high dynamic range. A receiver based on the frequency-folded ADC architecture is implemented in 65-nm CMOS and achieves a sample rate of 2-GS/s, a mean 49-dB SNDR, and 8.5-dB NF.
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