Novi aktivni leap-frog filtar trećeg reda

This paper presents the realization of third-order low-pass active-RC filters using a new Leap-Frog (LF) topology. New structure is a simplified LF structure with the elements calculated directly from the transfer function coefficients. Several versions of the circuits are presented and compared. The comparison to other common thirdorder filter sections is done, as well. The new LF filter has the reduced number of components, reduced complexity and straightforward design procedure compared to classical filters. As an illustration of the efficiency of the proposed new LF filter, the sensitivity analysis using Schoeffler sensitivity measure as well as output thermal noise analysis was performed on examples with Butterworth and Chebyshev 0.5dB pass-band ripple transfer functions. Using PSpice with a TL081 opamp model, the filter performance is simulated and the results compared and verified by measurements on a discrete-component breadboard filter. All equations needed for the step-by-step design are given.U radu je predstavljena realizacija nisko-propusnog aktivnog-RC filtra trećeg reda koji upotrebljava novu "leap-frog" (LF) topologiju. Nova struktura je pojednostavljena LF struktura s elementima koji se računaju direktno iz koeficijenata prijenosne funkcije. Nekoliko inačica krugova je prikazano i obavljena je usporedba. Napravljena je usporedba tako.er i s drugim uobičajenim filtarskim sekcijama trećeg reda. Novi LF filtar ima smanjeni broj komponenata, smanjenu kompleksnost i jednostavniji postupak projektiranja u usporedbi s klasičnim filtrima. Za ilustraciju učinkovitosti predstavljenog novog LF filtra, provedena je analiza osjetljivosti pomoću Schoefflerove mjere osjetljivosti i analiza termičkog šuma na izlazu na primjerima s prijenosnim funkcijama po Butterworthu i Chebyshevu s valovitošću u području propuštanja od 0.5 dB. Pomoću PSpice-a s modelom pojačala TL081, filtarska svojstva su simulirana, uspore.ena i potvr.ena mjerenjima na filtrima realiziranim pomoću diskretnih elemenata na štampanoj pločici. U radu su dane sve potrebne jednadžbe u postupku projektiranja korak po korak

Active Frequency Filters for Higher Frequencies

Práce pojednává o syntéze a optimalizaci kmitočtových analogových filtrů s moderními aktivními prvky užitých pro vyšší frekvence. Práce je rozdělena do tří částí, první část se zabývá problematikou týkající se kombinované ARC struktury Leap-Frog. Tato metoda není vzhledem k složitému návrhu řádně popsána a využívána v praktické rovině, přestože vykazuje např. nízké citlivosti. Pro rozšíření této metody byla nejprve provedena kompletní analýza jednotlivých typů filtrů pro zakončení typu a T a následné poznatky byly využity při implementaci této metody do programu NAF. V závěru byly zrealizovány vzorky reálných filtrů pro ověření funkčnosti a správného návrhu. Dalším velice zajímavým tématem v oblasti filtrů je využití vázaných pásmových propustí pro malé šířky pásma, kde je především nutné řešit problematiku týkající se poměru hodnot stavebních prvků, ale také ceny, kvality, rozměru cívek, citlivostí, činitelů jakosti, koeficientů atd. Proto se v praxi velice často nahrazuje cívka v obvodech RLC jinými ekvivalentními ztrátovými nebo bezeztrátovými bloky, které vytvářejí strukturu filtrů ARC. Zde byl především popsán návrh a možnost využití ztrátových uzemněných prvků jako jsou syntetické induktory a kmitočtově závislé negativní rezistory. Součásti návrhu jsou jednotlivé počítačové citlivostní analýzy, vymezení pásma použitelnosti a porovnání vlastností jednotlivých ztrátových uzemněných bloků. Kromě toho byl vytvořen pro tyto prvky program, který slouží k rychlému návrhu a zobrazení modulových a fázových kmitočtových charakteristik. Třetí část se zabývá využitím laditelných univerzálních filtrů obsahující tři či více operačních zesilovačů, čímž je zajištěna jejich univerzálnost a možnost vytvářet různé druhy přenosových charakteristik. V praxi jsou nejvíce využívány dva typy univerzálních filtrů, a to Akerberg - Mossberg a Kerwin - Huelsman - Newcomb, ke kterým bylo vztaženo porovnávání dalších méně známých univerzálních filtrů. V závěru byla ukázána možnost digitálního ladění univerzálního filtru pomocí digitálních potenciometrů pro filtr 10. řádu a kmitočet okolo 1 MHz.This thesis deals with the synthesis and optimization of frequency analogue filters with modern active elements usable for higher frequencies. The thesis is divided into three parts, the first part deals with the problematic concerning Leap-Frog combined ARC structure. Due to a difficult design, this method is not described in a detail and used in practice, although it shows e.g. low sensitivity. Firstly, a complete analysis of individual filters was made (for and T endings) and consequently these findings were used during implementation of this method to NAF program. Finally, samples of real filters were realized (for verification of functioning and correct design). Another very interesting topic concerning filters is usage of coupled band-pass for small bandwidth, where it is necessary to solve the problems concerning ratio of building elements values, but also price, quality, size of coils, sensitivity, Q factors, coefficients etc. That is why in practice a coil is very often substituted with other equivalent lossy and lossless blocks which create ARC filters structure. The design and the possibility of usage of lossy grounded elements were described here (such as synthetic inductors, frequency dependent negative resistor). Some parts of the design are individual computer sensitivity analysis, setting of usage and quality comparison of individual lossy grounded blocks. Besides, a program for these elements was created, it is useful for a quick design and depiction of transfer characteristics. The third part deals with the usage of tuning universal filters consisting three or more operational amplifiers, which secures its universality and possibility to create different kinds of transfer characteristic. In practice, Akerberg - Mossberg and Kerwin - Huelsman - Newcomb are the most used types of filters. These were also compared with less common universal filters. In the end, the possibility of digital tuning of universal filter with the help of digital potentiometers for filters of 10th order and frequency around 1 MHz was shown.

Resource allocation technique for powerline network using a modified shuffled frog-leaping algorithm

Resource allocation (RA) techniques should be made efficient and optimized in order to enhance the QoS (power & bit, capacity, scalability) of high-speed networking data applications. This research attempts to further increase the efficiency towards near-optimal performance. RA’s problem involves assignment of subcarriers, power and bit amounts for each user efficiently. Several studies conducted by the Federal Communication Commission have proven that conventional RA approaches are becoming insufficient for rapid demand in networking resulted in spectrum underutilization, low capacity and convergence, also low performance of bit error rate, delay of channel feedback, weak scalability as well as computational complexity make real-time solutions intractable. Mainly due to sophisticated, restrictive constraints, multi-objectives, unfairness, channel noise, also unrealistic when assume perfect channel state is available. The main goal of this work is to develop a conceptual framework and mathematical model for resource allocation using Shuffled Frog-Leap Algorithm (SFLA). Thus, a modified SFLA is introduced and integrated in Orthogonal Frequency Division Multiplexing (OFDM) system. Then SFLA generated random population of solutions (power, bit), the fitness of each solution is calculated and improved for each subcarrier and user. The solution is numerically validated and verified by simulation-based powerline channel. The system performance was compared to similar research works in terms of the system’s capacity, scalability, allocated rate/power, and convergence. The resources allocated are constantly optimized and the capacity obtained is constantly higher as compared to Root-finding, Linear, and Hybrid evolutionary algorithms. The proposed algorithm managed to offer fastest convergence given that the number of iterations required to get to the 0.001% error of the global optimum is 75 compared to 92 in the conventional techniques. Finally, joint allocation models for selection of optima resource values are introduced; adaptive power and bit allocators in OFDM system-based Powerline and using modified SFLA-based TLBO and PSO are propose

Velocity estimation via registration-guided least-squares inversion

This paper introduces an iterative scheme for acoustic model inversion where the notion of proximity of two traces is not the usual least-squares distance, but instead involves registration as in image processing. Observed data are matched to predicted waveforms via piecewise-polynomial warpings, obtained by solving a nonconvex optimization problem in a multiscale fashion from low to high frequencies. This multiscale process requires defining low-frequency augmented signals in order to seed the frequency sweep at zero frequency. Custom adjoint sources are then defined from the warped waveforms. The proposed velocity updates are obtained as the migration of these adjoint sources, and cannot be interpreted as the negative gradient of any given objective function. The new method, referred to as RGLS, is successfully applied to a few scenarios of model velocity estimation in the transmission setting. We show that the new method can converge to the correct model in situations where conventional least-squares inversion suffers from cycle-skipping and converges to a spurious model.Comment: 20 pages, 13 figures, 1 tabl

Variational-based data assimilation to simulate sediment concentration in the Lower Yellow River, China

The heavy sediment load of the Yellow River makes it difficult to simulate sediment concentration using classic numerical models. In this paper, on the basis of the classic one-dimensional numerical model of open channel flow, a variational-based data assimilation method is introduced to improve the simulation accuracy of sediment concentration and to estimate parameters in sediment carrying capacity. In this method, a cost function is introduced first to determine the difference between the sediment concentration distributions and available field observations. A one-dimensional suspended sediment transport equation, assumed as a constraint, is integrated into the cost function. An adjoint equation of the data assimilation system is used to solve the minimum problem of the cost function. Field data observed from the Yellow River in 2013 are used to test the proposed method. When running the numerical model with the data assimilation method, errors between the calculations and the observations are analyzed. Results show that (1) the data assimilation system can improve the prediction accuracy of suspended sediment concentration; (2) the variational inverse data assimilation is an effective way to estimate the model parameters, which are poorly known in previous research; and (3) although the available observations are limited to two cross sections located in the central portion of the study reach, the variational-based data assimilation system has a positive effect on the simulated results in the portion of the model domain in which no observations are available

Nonlinearity and noise modeling of operational transconductance amplifiers for continuous time analog filters

A general framework for performance optimization of continuous-time OTA-C (Operational Transconductance Amplifier-Capacitor) filters is proposed. Efficient procedures for evaluating nonlinear distortion and noise valid for any filter of arbitrary order are developed based on the matrix description of a general OTA-C filter model . Since these procedures use OTA macromodels, they can be used to obtain the results significantly faster than transistor-level simulation. In the case of transient analysis, the speed-up may be as much as three orders of magnitude without almost no loss of accuracy. This makes it possible to carry out direct numerical optimization of OTA-C filters with respect to important characteristics such as noise performance, THD, IM3, DR or SNR. On the other hand, the general OTA-C filter model allows us to apply matrix transforms that manipulate (rescale) filter element values and/or change topology without changing its transfer function. The above features are a basis to build automated optimization procedures for OTA-C filters. In particular, a systematic optimization procedure using equivalence transformations is proposed. The research also proposes suitable software implementations of the optimization process. The first part of the research proposes a general performance optimization procedure and to verify the process two application type examples are mentioned. An application example of the proposed approach to optimal block sequencing and gain distribution of 8th order cascade Butterworth filter (for two variants of OTA topologies) is given. Secondly the modeling tool is used to select the best suitable topology for a 5th order Bessel Low Pass Filter. Theoretical results are verified by comparing to transistor-level simulation withCADENCE. For the purpose of verification, the filters have also been fabricated in standard 0.5mm CMOS process. The second part of the research proposes a new linearization technique to improve the linearity of an OTA using an Active Error Feedforward technique. Most present day applications require very high linear circuits combined with low noise and low power consumption. An OTA based biquad filter has also been fabricated in 0.35mm CMOS process. The measurement results for the filter and the stand alone OTA have been discussed. The research focuses on these issues

Turbulence: Numerical Analysis, Modelling and Simulation

The problem of accurate and reliable simulation of turbulent flows is a central and intractable challenge that crosses disciplinary boundaries. As the needs for accuracy increase and the applications expand beyond flows where extensive data is available for calibration, the importance of a sound mathematical foundation that addresses the needs of practical computing increases. This Special Issue is directed at this crossroads of rigorous numerical analysis, the physics of turbulence and the practical needs of turbulent flow simulations. It seeks papers providing a broad understanding of the status of the problem considered and open problems that comprise further steps

Chronological Inversion Method for the Dirac Matrix in Hybrid Monte Carlo

In Hybrid Monte Carlo simulations for full QCD, the gauge fields evolve smoothly as a function of Molecular Dynamics time. Here we investigate improved methods of estimating the trial or starting solutions for the Dirac matrix inversion as superpositions of a chronological sequence of solutions in the recent past. By taking as the trial solution the vector which minimizes the residual in the linear space spanned by the past solutions, the number of conjugate gradient iterations per unit MD time is decreased by at least a factor of 2. Extensions of this basic approach to precondition the conjugate gradient iterations are also discussed.Comment: 35 pages, 18 EPS figures A new "preconditioning" method, derived from the Chronological Inversion, is described. Some new figures are appended. Some reorganization of the material has taken plac

Active Collaborative Localization in Heterogeneous Robot Teams

Accurate and robust state estimation is critical for autonomous navigation of robot teams. This task is especially challenging for large groups of size, weight, and power (SWAP) constrained aerial robots operating in perceptually-degraded GPS-denied environments. We can, however, actively increase the amount of perceptual information available to such robots by augmenting them with a small number of more expensive, but less resource-constrained, agents. Specifically, the latter can serve as sources of perceptual information themselves. In this paper, we study the problem of optimally positioning (and potentially navigating) a small number of more capable agents to enhance the perceptual environment for their lightweight,inexpensive, teammates that only need to rely on cameras and IMUs. We propose a numerically robust, computationally efficient approach to solve this problem via nonlinear optimization. Our method outperforms the standard approach based on the greedy algorithm, while matching the accuracy of a heuristic evolutionary scheme for global optimization at a fraction of its running time. Ultimately, we validate our solution in both photorealistic simulations and real-world experiments. In these experiments, we use lidar-based autonomous ground vehicles as the more capable agents, and vision-based aerial robots as their SWAP-constrained teammates. Our method is able to reduce drift in visual-inertial odometry by as much as 90%, and it outperforms random positioning of lidar-equipped agents by a significant margin. Furthermore, our method can be generalized to different types of robot teams with heterogeneous perception capabilities. It has a wide range of applications, such as surveying and mapping challenging dynamic environments, and enabling resilience to large-scale perturbations that can be caused by earthquakes or storms.Comment: To appear in Robotics: Science and Systems (RSS) 202