13,229 research outputs found
Controllable Fractional-Order Analogue Electronic Circuits
DisertaÄnĂ prĂĄce se zabĂ˝vĂĄ syntĂŠzou a analĂ˝zou novĂ˝ch obvodovĂ˝ch struktur neceloÄĂselnĂŠho (fraktĂĄlnĂho) ĹĂĄdu s ĹiditelnĂ˝mi parametry. HlavnĂ cĂl tĂŠto prĂĄce je nĂĄvrh novĂ˝ch ĹeĹĄenĂ filtraÄnĂch struktur fraktĂĄlnĂho ĹĂĄdu v proudovĂŠm mĂłdu, emulĂĄtorĹŻ prvkĹŻ fraktĂĄlnĂho ĹĂĄdu a takĂŠ oscilĂĄtorĹŻ. PrĂĄce obsahuje nĂĄvrh tĹĂ emulĂĄtorĹŻ pasivnĂho prvku fraktĂĄlnĂho ĹĂĄdu, tĹi filtraÄnĂ struktury a dva oscilĂĄtory navrĹženĂŠ na zĂĄkladÄ vyuĹžitĂ pasivnĂho prvku fraktĂĄlnĂho ĹĂĄdu v jejich obvodovĂŠ struktuĹe a dvÄ obecnĂŠ koncepce filtrĹŻ fraktĂĄlnĂho ĹĂĄdu zaloĹženĂŠ na vyuĹžitĂ aproximace pĹenosovĂŠ funkce fraktĂĄlnĂho ĹĂĄdu. Na zĂĄkladÄ obecnĂ˝ch koncepcĂ jsou v prĂĄci navrĹženy filtry fraktĂĄlnĂho ĹĂĄdu typu dolnĂ a hornĂ propust. DĂky aktivnĂm prvkĹŻm s pĹeladitelnĂ˝mi parametry, kterĂŠ jsou uĹžity v obvodovĂ˝ch strukturĂĄch je zajiĹĄtÄna Ĺiditelnost ĹĂĄdu filtru, jeho pĂłlovĂŠho kmitoÄtu a nÄkterĂ˝ch pĹĂpadech i Äinitele jakosti. Vlastnosti vĹĄech zapojenĂ jsou ovÄĹeny poÄĂtaÄovĂ˝mi simulacemi za pomoci behavioralnĂch simulaÄnĂch modelĹŻ aktivnĂch prvkĹŻ. NÄkterĂŠ z uvedenĂ˝ch obvodĹŻ byly realizovĂĄny na DPS a jejich vlastnosti ovÄĹeny experimentĂĄlnĂm mÄĹenĂm.The doctoral thesis focuses on the synthesis and analysis of novel non-integer-order (fractional-order) circuit structures with electronically adjustable parameters. The main goal of the thesis is the design of new solutions of fractional-order current-mode filtering structures, fractional-order passive elements and also oscillators. The thesis contains the designs of three emulators of fractional-order elements, three filtering structures and two oscillators based on the usage of a fractional-order passive element in their circuit structure, and two general conceptions of fractional-order filters based on an approximation of the fractional-order transfer function. Based on general conceptions of the filtering structures, the fractional-order low-pass and high-pass filters are designed. The adjustability of the order, the pole frequency and in several cases also the quality factor of the proposed circuits is provided by used active elements with adjustable parameters. The features of the proposed circuits are verified by simulations using behavioural simulation models of the active elements. Several of these circuits were implemented on PCB and verified by laboratory measurement.
Optimized Quality Factor of Fractional Order Analog Filters with Band-Pass and Band-Stop Characteristics
Fractional order (FO) filters have been investigated in this paper, with
band-pass (BP) and band-stop (BS) characteristics, which can not be achieved
with conventional integer order filters with orders lesser then two. The
quality factors for symmetric and asymmetric magnitude response have been
optimized using real coded Genetic Algorithm (GA) for a user specified center
frequency. Parametric influence of the FO filters on the magnitude response is
also illustrated with credible numerical simulations.Comment: 6 pages, 13 figures; 2012 Third International Conference on
Computing, Communication and Networking Technologies (ICCCNT'12), July 2012,
Coimbator
BICEP2 II: Experiment and Three-Year Data Set
We report on the design and performance of the BICEP2 instrument and on its
three-year data set. BICEP2 was designed to measure the polarization of the
cosmic microwave background (CMB) on angular scales of 1 to 5 degrees
(=40-200), near the expected peak of the B-mode polarization signature of
primordial gravitational waves from cosmic inflation. Measuring B-modes
requires dramatic improvements in sensitivity combined with exquisite control
of systematics. The BICEP2 telescope observed from the South Pole with a 26~cm
aperture and cold, on-axis, refractive optics. BICEP2 also adopted a new
detector design in which beam-defining slot antenna arrays couple to
transition-edge sensor (TES) bolometers, all fabricated on a common substrate.
The antenna-coupled TES detectors supported scalable fabrication and
multiplexed readout that allowed BICEP2 to achieve a high detector count of 500
bolometers at 150 GHz, giving unprecedented sensitivity to B-modes at degree
angular scales. After optimization of detector and readout parameters, BICEP2
achieved an instrument noise-equivalent temperature of 15.8 K sqrt(s). The
full data set reached Stokes Q and U map depths of 87.2 nK in square-degree
pixels (5.2 K arcmin) over an effective area of 384 square degrees within
a 1000 square degree field. These are the deepest CMB polarization maps at
degree angular scales to date. The power spectrum analysis presented in a
companion paper has resulted in a significant detection of B-mode polarization
at degree scales.Comment: 30 pages, 24 figure
The Beauty of Symmetry: Common-mode rejection filters for high-speed interconnects and balanced microwave circuits
Common-mode rejection filters operating at microwave frequencies have been the
subject of intensive research activity in the last decade. These filters are of interest for
the suppression of common-mode noise in high-speed digital circuits, where differential
signals are widely employed due to the high immunity to noise, electromagnetic
interference (EMI) and crosstalk of differential-mode interconnects. These filters can
also be used to improve common-mode rejection in microwave filters and circuits
dealing with differential signals. Ideally, common-mode stopband filters should be
transparent for the differential mode from DC up to very high frequencies (all-pass),
should preserve the signal integrity for such mode, and should exhibit the widest and
deepest possible rejection band for the common mode in the region of interest.
Moreover, these characteristics should be achieved by means of structures with the
smallest possible size. In this article, several techniques for the implementation of
common-mode suppression filters in planar technology are reviewed. In all the cases,
the strategy to simultaneously achieve common-mode suppression and all-pass behavior
for the differential mode is based on selective mode-suppression. This selective mode
suppression (either the common or the differential mode) in balanced lines is typically
(although not exclusively) achieved by symmetrically loading the lines with symmetric
resonant elements, opaque for the common-mode and transparent for the differential
mode (common-mode suppression), or vice versa (differential-mode suppression).MINECO, Spain-TEC2013-40600-R, TEC2013-41913-PGeneralitat de Catalunya-2014SGR-15
Systems control theory applied to natural and synthetic musical sounds
Systems control theory is a far developped field which helps to study stability, estimation and control of dynamical systems. The physical behaviour of musical instruments, once described by dynamical systems, can then be controlled and numerically simulated for many purposes.
The aim of this paper is twofold: first, to provide the theoretical background on linear system theory, both in continuous and discrete time, mainly in the case of a finite number of degrees of freedom ; second, to give illustrative examples on wind instruments, such as the vocal tract represented as a waveguide, and a sliding flute
Current mode fractional order filters using VDTAs with Grounded capacitors
In this work, the design of current mode Fractional order filter using VDTAs (Voltage differencing trans-conductance amplifier) as an active element with grounded capacitors has been proposed. The approximate transfer functions of low and high pass filters of fractional order on the basis of the integer order transfer has been shown and the form of those functions of filters is also implemented using VDTA as an active building block. In this work, filters of the different sequence have been realized. The frequency domain simulation results of the proposed filters are obtained on Matlab and PSPICE with TSMC CMOS 180 nm technology parameters. Stability and sensitivity is also verifie
Simulations of Incompressible MHD Turbulence
We simulate incompressible MHD turbulence in the presence of a strong
background magnetic field. Our major conclusions are: 1) MHD turbulence is most
conveniently described in terms of counter propagating shear Alfven and slow
waves. Shear Alfven waves control the cascade dynamics. Slow waves play a
passive role and adopt the spectrum set by the shear Alfven waves, as does a
passive scalar. 2) MHD turbulence is anisotropic with energy cascading more
rapidly along k_perp than along k_parallel, where k_perp and k_parallel refer
to wavevector components perpendicular and parallel to the local magnetic
field. Anisotropy increases with increasing k_perp. 3) MHD turbulence is
generically strong in the sense that the waves which comprise it suffer order
unity distortions on timescales comparable to their periods. Nevertheless,
turbulent fluctuations are small deep inside the inertial range compared to the
background field. 4) Decaying MHD turbulence is unstable to an increase of the
imbalance between the flux of waves propagating in opposite directions along
the magnetic field. 5) Items 1-4 lend support to the model of strong MHD
turbulence by Goldreich & Sridhar (GS). Results from our simulations are also
consistent with the GS prediction gamma=2/3. The sole notable discrepancy is
that 1D power law spectra, E(k_perp) ~ k_perp^{-alpha}, determined from our
simulations exhibit alpha ~ 3/2, whereas the GS model predicts alpha = 5/3.Comment: 56 pages, 30 figures, submitted to ApJ 59 pages, 31 figures, accepted
to Ap
Multiple Order Dual-Band Active Ring Filters with Composite Right/Left Handed Cells
In this paper, a novel dual-band active filter topology is presented. The non-linear phase response of a composite right/left-handed cell is used to achieve the desired dual-band performance. Additionally, the proposed structure based on coupled ring resonators yields a very compact solution in which high-order implementations can be easily obtained by cascading multiple rings. The theoretical principles of this type of filters are analyzed in detail. Finally, three prototypes based on first-, second- and third-order structures validate the feasibility of this type of filters. Good agreement between simulations and measurements has been achieved
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