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

Recent Advances in Variable Digital Filters

Variable digital filters are widely used in a number of applications of signal processing because of their capability of self-tuning frequency characteristics such as the cutoff frequency and the bandwidth. This chapter introduces recent advances on variable digital filters, focusing on the problems of design and realization, and application to adaptive filtering. In the topic on design and realization, we address two major approaches: one is the frequency transformation and the other is the multi-dimensional polynomial approximation of filter coefficients. In the topic on adaptive filtering, we introduce the details of adaptive band-pass/band-stop filtering that include the well-known adaptive notch filtering

Low complexity and efficient dynamic spectrum learning and tunable bandwidth access for heterogeneous decentralized cognitive radio networks

International audienceThis paper deals with the design of the low complexity and efficient dynamic spectrum learning and access (DSLA) scheme for next-generation heterogeneous decentralized Cognitive Radio Networks (CRNs) such as Long Term Evolution-Advanced and 5G. Existing DSLA schemes for decentralized CRNs are focused predominantly on the decision making policies which perform the task of orthogonalization of secondary users to optimum vacant subbands of fixed bandwidth. The focus of this paper is the design of DSLA scheme for decentralized CRNs to support the tunable vacant bandwidth requirements of the secondary users while minimizing the computationally intensive subband switchings. We first propose a new low complexity VDF which is designed by modifying second order frequency transformation and subsequently combining it with the interpolation technique. It is referred to as Interpolation and Modified Frequency Transformation based VDF (IMFT-VDF) and it provides tunable bandpass responses anywhere over Nyquist band with complete control over the bandwidth as well as the center frequency. Second, we propose a tunable decision making policy, ρt_randρt_rand, consisting of learning and access unit, and is designed to take full advantage of exclusive frequency response control offered by IMFT-VDF. The simulation results verify the superiority of the proposed DSLA scheme over the existing DSLA schemes while complexity comparisons indicate total gate count savings from 11% to as high as 87% over various existing schemes. Also, lower number of subband switchings make the proposed scheme power-efficient and suitable for battery-operated cognitive radio terminals

System- and Data-Driven Methods and Algorithms

An increasing complexity of models used to predict real-world systems leads to the need for algorithms to replace complex models with far simpler ones, while preserving the accuracy of the predictions. This two-volume handbook covers methods as well as applications. This first volume focuses on real-time control theory, data assimilation, real-time visualization, high-dimensional state spaces and interaction of different reduction techniques

Development and experimental validation of direct controller tuning for spaceborne telescopes

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2000.Includes bibliographical references (p. 285-294).Strict requirements in the performance of future space-based observatories such as the Space Interferometry Mission (SIM) and the Next Generation Space Telescope (NGST), will extend the state-of-the-art of critical mission spaceflight-proven active control design. A control design strategy, which combines the high performance and stability robustness guarantees of modem, robust-control design with the spaceflight heritage of conventional control design, is proposed which will meet the strict requirements and maintain traceability to the successful controllers from predecessor spacecraft. Two principal tools are developed: an analysis algorithm that quantifies each sensor/actuator combination's effectiveness for control, and a design engine which tunes a baseline controller to improve performance and/or stability robustness. The sensor/actuator effectiveness indexing tool requires a reduced-order state-space model of the plant. A modification of the balanced reduction method is introduced which improves numerical conditioning so that the order of large models of flexible spacecraft may be decreased. For each sensor and actuator an index is computed using the modal controllability from an actuator weighted by the modal cost in the performance, and the model observability of a sensor weighted by the modal cost of the disturbance. The special case of actuators that are used for active output isolation is handled separately. The designer makes use of the sensor/actuator indexing tool to select which control channels to emphasize in the tuning. The tuning tool is based on forming an augmented cost from weighting performance, stability robustness, deviation from the baseline controller, and controller gain. The tuning algorithm can operate with the plant's state-space design model or directly with the plant's measured frequency-response data. Two differentiable multivariable stability robustness metrics are formed, one based on the maximum singular value of the Sensitivity transfer matrix and one based on the multivariable Nyquist locus. The controller is parameterized with a general tridiagonal parameterization based on the real-modal state-space form. The augmented cost is chosen to be differentiable and a closed-loop stability-preserving unconstrained nonlinear descent program is used to directly compute controller parameters that decrease the augmented cost. To automate the closed-loop stability determination in the measured-data-based designs, a rule-based algorithm is created to invoke the multivariable Nyquist stability criteria. The use of the tuning technique is placed in context with a high-level control design methodology. The tuning technique is evaluated on a sample problem and then experimentally demonstrated on a laboratory test article with dynamics, sensor suite, and actuator suite all similar to future spaceborne observatories. The developed test article is the first spacetelescope- like experimental facility to combine large-angle slewing with nanometer optical phasing and sub-arcsecond pointing in the presence of spacecraft-like disturbances. The technique is applied to generate an improved controller for a model of the SIM spacecraft.by Gregory J.W. Mallory.Ph.D