7,453 research outputs found
High Frequency Quantum Admittance and Noise Measurement with an On-chip Resonant Circuit
By coupling a quantum detector, a superconductor-insulator-superconductor
junction, to a Josephson junction \textit{via} a resonant circuit we probe the
high frequency properties, namely the ac complex admittance and the current
fluctuations of the Josephson junction at the resonant frequencies. The
admittance components show frequency dependent singularities related to the
superconducting density of state while the noise exhibits a strong frequency
dependence, consistent with theoretical predictions. The circuit also allows to
probe separately the emission and absorption noise in the quantum regime of the
superconducting resonant circuit at equilibrium. At low temperature the
resonant circuit exhibits only absorption noise related to zero point
fluctuations, whereas at higher temperature emission noise is also present.Comment: 15 pages, 15 figure
CMOS-Compatible Room-Temperature Rectifier Toward Terahertz Radiation Detection
In this paper, we present a new rectifying device, compatible with the technology of CMOS image sensors, suitable for implementing a direct-conversion detector operating at room temperature for operation at up to terahertz frequencies. The rectifying device can be obtained by introducing some simple modifications of the charge-storage well in conventional CMOS integrated circuits, making the proposed solution easy to integrate with the existing imaging systems. The rectifying device is combined with the different elements of the detector, composed of a 3D high-performance antenna and a charge-storage well. In particular, its position just below the edge of the 3D antenna takes maximum advantage of the high electric field concentrated by the antenna itself. In addition, the proposed structure ensures the integrity of the charge-storage well of the detector. In the structure, it is not necessary to use very scaled and costly technological nodes, since the CMOS transistor only provides the necessary integrated readout electronics. On-wafer measurements of RF characteristics of the designed junction are reported and discussed. The overall performances of the entire detector in terms of noise equivalent power (NEP) are evaluated by combining low-frequency measurements of the rectifier with numerical simulations of the 3D antenna and the semiconductor structure at 1Â THz, allowing prediction of the achievable NEP
Detecting Current Noise with a Josephson Junction in the Macroscopic Quantum Tunneling Regime
We discuss the use of a hysteretic Josephson junction to detect current
fluctuations with frequencies below the plasma frequency of the junction. These
adiabatic fluctuations are probed by switching measurements observing the
noise-affected average rate of macroscopic quantum tunneling of the detector
junction out of its zero-voltage state. In a proposed experimental scheme,
frequencies of the noise are limited by an on-chip filtering circuit. The third
cumulant of current fluctuations at the detector is related to an asymmetry of
the switching rates.Comment: 26 pages, 10 figures. To appear in Journal of Low Temperature Physics
in the proceedings of the ULTI conference organized in Lammi, Finland (2006
Suspensions Thermal Noise in the LIGO Gravitational Wave Detector
We present a calculation of the maximum sensitivity achievable by the LIGO
Gravitational wave detector in construction, due to limiting thermal noise of
its suspensions. We present a method to calculate thermal noise that allows the
prediction of the suspension thermal noise in all its 6 degrees of freedom,
from the energy dissipation due to the elasticity of the suspension wires. We
show how this approach encompasses and explains previous ways to approximate
the thermal noise limit in gravitational waver detectors. We show how this
approach can be extended to more complicated suspensions to be used in future
LIGO detectors.Comment: 28 pages, 13 figure
On the Exploitation of Admittance Measurements for Wired Network Topology Derivation
The knowledge of the topology of a wired network is often of fundamental
importance. For instance, in the context of Power Line Communications (PLC)
networks it is helpful to implement data routing strategies, while in power
distribution networks and Smart Micro Grids (SMG) it is required for grid
monitoring and for power flow management. In this paper, we use the
transmission line theory to shed new light and to show how the topological
properties of a wired network can be found exploiting admittance measurements
at the nodes. An analytic proof is reported to show that the derivation of the
topology can be done in complex networks under certain assumptions. We also
analyze the effect of the network background noise on admittance measurements.
In this respect, we propose a topology derivation algorithm that works in the
presence of noise. We finally analyze the performance of the algorithm using
values that are typical of power line distribution networks.Comment: A version of this manuscript has been submitted to the IEEE
Transactions on Instrumentation and Measurement for possible publication. The
paper consists of 8 pages, 11 figures, 1 tabl
In-place recalibration technique applied to a capacitance-type system for measuring rotor blade tip clearance
The rotor blade tip clearance measurement system consists of a capacitance sensing probe with self contained tuning elements, a connecting coaxial cable, and remotely located electronics. Tests show that the accuracy of the system suffers from a strong dependence on probe tip temperature and humidity. A novel inplace recalibration technique was presented which partly overcomes this problem through a simple modification of the electronics that permits a scale factor correction. This technique, when applied to a commercial system significantly reduced errors under varying conditions of humidity and temperature. Equations were also found that characterize the important cable and probe design quantities
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