22,973 research outputs found
Preliminary design study of a regenerative life support system information management and display system
The instrumentation requirements for a regenerative life support systems were studied to provide the earliest possible indication of a malfunction that will permit degradation of the environment. Four categories of parameters were investigated: environmental parameters that directly and immediately influence the health and safety of the cabin crew; subsystems' inputs to the cabin that directly maintain the cabin environmental parameters; indications for maintenance or repair; and parameters useful as diagnostic indicators. A data averager concept is introduced which provides a moving average of parameter values that is not influenced by spurious changes, and is convenient for detecting parameter rates of change. A system is included to provide alarms at preselected parameter levels
CMOS OTA-C high-frequency sinusoidal oscillators
Several topology families are given to implement practical CMOS sinusoidal oscillators by using operational transconductance amplifier-capacitor (OTA-C) techniques. Design techniques are proposed taking into account the CMOS OTA's dominant nonidealities. Building blocks are presented for amplitude control, both by automatic gain control (AGC) schemes and by limitation schemes. Experimental results from 3- and 2- mu m CMOS (MOSIS) prototypes that exhibit oscillation frequencies of up to 69 MHz are obtained. The amplitudes can be adjusted between 1 V peak to peak and 100 mV peak to peak. Total harmonic distortions from 2.8% down to 0.2% have been measured experimentally.Comisión Interministerial de Ciencia y Tecnología ME87-000
CMOS design of chaotic oscillators using state variables: a monolithic Chua's circuit
This paper presents design considerations for monolithic implementation of piecewise-linear (PWL) dynamic systems in CMOS technology. Starting from a review of available CMOS circuit primitives and their respective merits and drawbacks, the paper proposes a synthesis approach for PWL dynamic systems, based on state-variable methods, and identifies the associated analog operators. The GmC approach, combining quasi-linear VCCS's, PWL VCCS's, and capacitors is then explored regarding the implementation of these operators. CMOS basic building blocks for the realization of the quasi-linear VCCS's and PWL VCCS's are presented and applied to design a Chua's circuit IC. The influence of GmC parasitics on the performance of dynamic PWL systems is illustrated through this example. Measured chaotic attractors from a Chua's circuit prototype are given. The prototype has been fabricated in a 2.4- mu m double-poly n-well CMOS technology, and occupies 0.35 mm/sup 2/, with a power consumption of 1.6 mW for a +or-2.5-V symmetric supply. Measurements show bifurcation toward a double-scroll Chua's attractor by changing a bias current
Passive alignment stability and auto-alignment of multipass amplifiers based on Fourier transforms
The stability properties of Fourier-based multipass amplifier to
misalignments (tilts) of its optical components has been investigated. For this
purpose, a method to quantify the sensitivity to tilts based on the amplifier
small signal gain has been elaborated and compared with measurements. To
improve on the tilt stability by more than an order of magnitude a simple
auto-alignment system has been proposed and tested. This study, combined with
other investigations devoted to the stability of the output beam to variations
of aperture and thermal lens effects of the active medium, qualifies the
Fourier-based amplifier for the high-energy and the high-power sector.Comment: 10 pages, 11 figure
An Experiment and Detection Scheme for Cavity-based Cold Dark Matter Searches
A resonance detection scheme and some useful ideas for cavity-based searches
of light cold dark matter particles (such as axions) are presented, as an
effort to aid in the on-going endeavors in this direction as well as for future
experiments, especially in possibly developing a table-top experiment. The
scheme is based on our idea of a resonant detector, incorporating an integrated
Tunnel Diode (TD) and a GaAs HEMT/HFET (High Electron Mobility
Transistor/Heterogenous FET) transistor amplifier, weakly coupled to a cavity
in a strong transverse magnetic field. The TD-amplifier combination is
suggested as a sensitive and simple technique to facilitate resonance detection
within the cavity while maintaining excellent noise performance, whereas our
proposed Halbach magnet array could serve as a low-noise and permanent solution
replacing the conventional electromagnets scheme. We present some preliminary
test results which demonstrate resonance detection from simulated test signals
in a small optimal axion mass range with superior Signal-to-Noise Ratios (SNR).
Our suggested design also contains an overview of a simpler on-resonance dc
signal read-out scheme replacing the complicated heterodyne readout. We believe
that all these factors and our propositions could possibly improve or at least
simplify the resonance detection and read-out in cavity-based DM particle
detection searches (and other spectroscopy applications) and reduce the
complications (and associated costs), in addition to reducing the
electromagnetic interference and background.Comment: 22 pages, 7 figure
Accurate Settling-Time Modeling and Design Procedures for Two-Stage Miller-Compensated Amplifiers for Switched-Capacitor Circuits
We present modeling techniques for accurate estimation of settling errors in switched-capacitor (SC) circuits built with Miller-compensated operational transconductance amplifiers (OTAs). One distinctive feature of the proposal is the computation of the impact of signal levels (on both the model parameters and the model structure) as they change during transient evolution. This is achieved by using an event-driven behavioral approach that combines small- and large-signal behavioral descriptions and keeps track of the amplifier state after each clock phase. Also, SC circuits are modeled under closed-loop conditions to guarantee that the results remain close to those obtained by electrical simulation of the actual circuits. Based on these models, which can be regarded as intermediate between the more established small-signal approach and full-fledged simulations, design procedures for dimensioning SC building blocks are presented whose targets are system-level specifications (such as ENOB and SNDR) instead of OTA specifications. The proposed techniques allow to complete top-down model-based designs with 0.3-b accuracy.Ministerio de Educación y Ciencia TEC2006-03022Junta de Andalucía TIC-0281
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
Progress of analog-hybrid computation
Review of fast analog/hybrid computer systems, integrated operational amplifiers, electronic mode-control switches, digital attenuators, and packaging technique
Optimising the multiplex factor of the frequency domain multiplexed readout of the TES-based microcalorimeter imaging array for the X-IFU instrument on the Athena Xray observatory
Athena is a space-based X-ray observatory intended for exploration of the hot
and energetic universe. One of the science instruments on Athena will be the
X-ray Integrated Field Unit (X-IFU), which is a cryogenic X-ray spectrometer,
based on a large cryogenic imaging array of Transition Edge Sensors (TES) based
microcalorimeters operating at a temperature of 100mK. The imaging array
consists of 3800 pixels providing 2.5 eV spectral resolution, and covers a
field of view with a diameter of of 5 arc minutes. Multiplexed readout of the
cryogenic microcalorimeter array is essential to comply with the cooling power
and complexity constraints on a space craft. Frequency domain multiplexing has
been under development for the readout of TES-based detectors for this purpose,
not only for the X-IFU detector arrays but also for TES-based bolometer arrays
for the Safari instrument of the Japanese SPICA observatory. This paper
discusses the design considerations which are applicable to optimise the
multiplex factor within the boundary conditions as set by the space craft. More
specifically, the interplay between the science requirements such as pixel
dynamic range, pixel speed, and cross talk, and the space craft requirements
such as the power dissipation budget, available bandwidth, and electromagnetic
compatibility will be discussed
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