1,656 research outputs found
Harmonic analysis of oscillators through standard numerical continuation tools
In this paper, we describe a numerical continuation method that enables
harmonic analysis of nonlinear periodic oscillators. This method is formulated
as a boundary value problem that can be readily implemented by resorting to a
standard continuation package - without modification - such as AUTO, which we
used. Our technique works for any kind of oscillator, including electronic,
mechanical and biochemical systems. We provide two case studies. The first
study concerns itself with the autonomous electronic oscillator known as the
Colpitts oscillator, and the second one with a nonlinear damped oscillator, a
non-autonomous mechanical oscillator. As shown in the case studies, the
proposed technique can aid both the analysis and the design of the oscillators,
by following curves for which a certain constraint, related to harmonic
analysis, is fulfilled.Comment: 20 pages, 4 figure
Realization of Resistorless Lossless Positive and Negative Grounded Inductor Simulators Using Single ZC-CCCITA
This paper is in continuation with the very recent work of Prasad et al. [14], wherein new realizations of grounded and floating positive inductor simulator using current differencing transconductance amplifier (CDTA) are reported. The focus of the paper is to provide alternate realizations of lossless, both positive and negative inductor simulators (PIS and NIS) in grounded form using z-copy current-controlled current inverting transconductance amplifier (ZC-CCCITA), which can be considered as a derivative of CDTA, wherein the current differencing unit (CDU) is reduced to a current-controlled current inverting unit. We demonstrate that only a single ZC-CCCITA and one grounded capacitor are sufficient to realize grounded lossless PIS or NIS. The proposed circuits are resistorless whose parameters can be controlled through the bias currents. The workability of the proposed PIS is validated by SPICE simulations on three RLC prototypes
Quantum limits of cold damping with optomechanical coupling
Thermal noise of a mirror can be reduced by cold damping. The displacement is
measured with a high-finesse cavity and controlled with the radiation pressure
of a modulated light beam. We establish the general quantum limits of noise in
cold damping mechanisms and we show that the optomechanical system allows to
reach these limits. Displacement noise can be arbitrarily reduced in a narrow
frequency band. In a wide-band analysis we show that thermal fluctuations are
reduced as with classical damping whereas quantum zero-point fluctuations are
left unchanged. The only limit of cold damping is then due to zero-point energy
of the mirrorComment: 10 pages, 3 figures, RevTe
Stochastic Testing Simulator for Integrated Circuits and MEMS: Hierarchical and Sparse Techniques
Process variations are a major concern in today's chip design since they can
significantly degrade chip performance. To predict such degradation, existing
circuit and MEMS simulators rely on Monte Carlo algorithms, which are typically
too slow. Therefore, novel fast stochastic simulators are highly desired. This
paper first reviews our recently developed stochastic testing simulator that
can achieve speedup factors of hundreds to thousands over Monte Carlo. Then, we
develop a fast hierarchical stochastic spectral simulator to simulate a complex
circuit or system consisting of several blocks. We further present a fast
simulation approach based on anchored ANOVA (analysis of variance) for some
design problems with many process variations. This approach can reduce the
simulation cost and can identify which variation sources have strong impacts on
the circuit's performance. The simulation results of some circuit and MEMS
examples are reported to show the effectiveness of our simulatorComment: Accepted to IEEE Custom Integrated Circuits Conference in June 2014.
arXiv admin note: text overlap with arXiv:1407.302
Enabling High-Dimensional Hierarchical Uncertainty Quantification by ANOVA and Tensor-Train Decomposition
Hierarchical uncertainty quantification can reduce the computational cost of
stochastic circuit simulation by employing spectral methods at different
levels. This paper presents an efficient framework to simulate hierarchically
some challenging stochastic circuits/systems that include high-dimensional
subsystems. Due to the high parameter dimensionality, it is challenging to both
extract surrogate models at the low level of the design hierarchy and to handle
them in the high-level simulation. In this paper, we develop an efficient
ANOVA-based stochastic circuit/MEMS simulator to extract efficiently the
surrogate models at the low level. In order to avoid the curse of
dimensionality, we employ tensor-train decomposition at the high level to
construct the basis functions and Gauss quadrature points. As a demonstration,
we verify our algorithm on a stochastic oscillator with four MEMS capacitors
and 184 random parameters. This challenging example is simulated efficiently by
our simulator at the cost of only 10 minutes in MATLAB on a regular personal
computer.Comment: 14 pages (IEEE double column), 11 figure, accepted by IEEE Trans CAD
of Integrated Circuits and System
Passive Tracking System and Method
System and methods are disclosed for passively determining the location of a moveable transmitter utilizing a pair of phase shifts at a receiver for extracting a direction vector from a receiver to the transmitter. In a preferred embodiment, a phase difference between the transmitter and receiver is extracted utilizing a noncoherent demodulator in the receiver. The receiver includes antenna array with three antenna elements, which preferably are patch antenna elements placed apart by one-half wavelength. Three receiver channels are preferably utilized for simultaneously processing the received signal from each of the three antenna elements. Multipath transmission paths for each of the three receiver channels are indexed so that comparisons of the same multipath component are made for each of the three receiver channels. The phase difference for each received signal is determined by comparing only the magnitudes of received and stored modulation signals to determine a winning modulation symbol
Exact quantum dissipative dynamics under external time-dependent fields driving
Exact and nonperturbative quantum master equation can be constructed via the
calculus on path integral. It results in hierarchical equations of motion for
the reduced density operator. Involved are also a set of well--defined
auxiliary density operators that resolve not just system--bath coupling
strength but also memory. In this work, we scale these auxiliary operators
individually to achieve a uniform error tolerance, as set by the reduced
density operator. An efficient propagator is then proposed to the hierarchical
Liouville--space dynamics of quantum dissipation. Numerically exact studies are
carried out on the dephasing effect on population transfer in the simple
stimulated Raman adiabatic passage scheme. We also make assessments on several
perturbative theories for their applicabilities in the present system of study
S-band SBAW microwave source, phase 2
Results of aging experiments on 1.072 GHz SBAW oscillators are discussed as well as the design, fabrication and test of 2.143 GHz SBAW delay lines. Two design approaches were implemented. The third harmonic transducer on 36 deg rotated Y cut quartz proved to be the most useful design, whereas the fifth harmonic transducer on - 50 5 deg rotated Y cut quartz suffered from high insertion loss and poor sidelobe rejection. The construction and characterization of the 2 GHz SBAW oscillator are described. Phase noise, frequency dependence on temperature, and 6-month aging were measured. Some SAW and SBAW oscillators were compared as were both the 1 and 2 GHz oscillators. The 2 GHz SBAW oscillator showed significant improvement in phase noise and temperature stability over the 2 GHz SAW oscillator developed in previous NASA programs. A technique to produce SBAW delay lines of different frequencies from a single mask is examined. The delay lines were incorporated into oscillator circuits to demonstrate the ability to select the frequency output of the SBAW oscillator
A very high frequency radio interferometer for investigating ionospheric disturbances using geostationary satellites. Determination of changes in exospheric electron content by a comparison of group delay and Faraday rotation
The theory and development of a VHF correlation radio interferometer for investigating ionospheric disturbances are discussed. The system was developed to receive signals from the geostationary Applications Technology Satellites. Amplitude and phase variations of the signal passing through the ionosphere can be detected by this instrument. The system consists of two superheterodyne receivers separated by a distance known as the baseline of the system. Since the system is a phase sensitive instrument, the local oscillators of the two receivers must be phase coherent. This is accomplished by using phase-locked loops for generating the local oscillators. The two signals from the separate receivers are cross-correlated by multiplying the two signals together and then time averaging the result. The sensitivity of the instrument is increased by off-setting one of the local oscillators by a small amount
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