Search results for "FREQUENCY"

Echo cancellation system for iso-frequency repeaters : contribution to the development of a new generation digital repeater

2014

On-frequency repeaters are a cost-effective solution to extend coverage and enhance wireless communications, especially in shadow areas. However, coupling between the receiving antenna and the transmitting antenna, called radio frequency echo, increases modulation errors and creates oscillations in the system when the echo power is high. According to the communication standards, extremely weak echoes decrease the transmission rate, while strong echoes damage electroni ccircuits because of power peaks. This thesis aims at characterizing the echo phenomenon under different modulations, and proposing an optimized solution directly integrated to industry. We have turned to digital solutions esp…

Familial mediterranean fever gene (MEVF) mutations in Crohnʼs disease in a Mediterranean area

2008

Frequency-dependent response and dynamic disorder

1991

Abstract This paper discusses selected aspects of the application of dynamic percolation models to ionic transport in mixed-ion superionic conductors. The discussion is based on an AB lattice gas model with hard-core repulsions and a ratio of τ, 0 ⩽ τ ⩽ ∞, between the transition rates of particles A and B. The frequency-dependent conductivity for a tracer particle is calculated within an effective-medium theory. The motion of the background B-particles is regarded as providing a fluctuating disordered environment for the tracer particles A. A crossover frequency separating high-frequency and low-frequency response is found which scales with τ as ω c ∼ τ 1 2 . The results for the dc limit ar…

Robust model-following control of parallel UPS single-phase inverters

2008

This paper presents a robust control technique applied to modular uninterruptible power-supply (UPS) inverters operating in parallel. When compared to conventional proportional-integral (PI) control, the proposed technique improves the response of the output voltage to load steps and to high distorted output currents, reducing the distortion of the output voltage. Furthermore, an excellent distribution of currents between modules is achieved, resulting in fine power equalization between the inverters on stream. The crossover frequency of the different loop gains involved is moderate, so that robustness to variations of the operation point and to modeling uncertainties is achieved. A compara…

Radio frequency shielding of thin aluminized plastic filters investigated for the ATHENA X-IFU detector

2018

Copyright 2018 Society of Photo-Optical Instrumentation Engineers (SPIE). One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited. The X-ray Integral Field Unit (X-IFU) is one of the two detectors of the ATHENA astrophysics space mission approved by ESA in the Cosmic Vision 2015-2025 Science Programme. The X-IFU consists of a large array of transition edge sensors (TES) micro-calorimeters covering a field of view of 5' diameter, sensitive in the energy range 0.2-12 keV, and providing a spectral resolution…

The focal plane assembly for the Athena X-ray Integral Field Unit instrument

2016

This paper summarizes a preliminary design concept for the focal plane assembly of the X-ray Integral Field Unit on the Athena spacecraft, an imaging microcalorimeter that will enable high spectral resolution imaging and point-source spectroscopy. The instrument's sensor array will be a ~ 3840-pixel transition edge sensor (TES) microcalorimeter array, with a frequency domain multiplexed SQUID readout system allowing this large-format sensor array to be operated within the thermal constraints of the instrument's cryogenic system. A second TES detector will be operated in close proximity to the sensor array to detect cosmic rays and secondary particles passing through the sensor array for off…

Ferroelectricity in {N(CH3)4}2ZnI4

1988

Dielectric properties of the {N(CH 3 ) 4 } 2 ZnI 4 crystal were studied between room temperature and 4.2 K. Two phase transitions were seen from dielectric constant anomalies at T 1 =254 K and T c =210 K on cooling. Ferroelectric hysteresis loops were observed along the c -direction below T c with a low frequency applied field of 0.0025 Hz. The spontaneous polarization obtained by pyroelectric charge measurement tended to be 2.5×10 -3 C/m 2 at 0 K.

Der Einfluß von Trichlormethan auf die δ-Relaxation eines kristallin-flüssigen Seitenkettenpolymers

1986

Dielektrische Untersuchungen an flussig-kristallinen Polymeren, in denen die Flussigkristalleinheit in der Seitenkette angeordnet ist, wurden von 10 Hz bis 100 kHz bei unterschiedlichen Temperaturen durchgefuhrt. Es konnte gezeigt werden, das sowohl die Relaxationsfrequenz als auch die Geometrie der Absorptionskurven der δ-Relaxation (Reorientierung der Seitenkette infolge der segmentalen Beweglichkeit der Hauptkette) durch Zugabe von Trichlormethan verandert werden. Trichlormethan wirkt als Weichmacher. Bei langerer Lagerung verdunstet das Trichlormethan und die molekulare Beweglichkeit vermindert sich. Dielectric investigations on liquid-crystalline polymers with the liquid crystal unit p…

Statistical Properties of Generalized Strain Criterion for Multiaxial Random Fatigue

1989

ABSTRACT Statistical properties of generalized criterion of the maximum shear and normal strains on the fracture plane have been presented, Functions of probability distribution and spectral density of the equivalent strain have been analysed on the assumption that a random tensor of strain state is a six-dimensional stationary and ergodic Gaussian process. The expected value and variance of the equivalent strain have been determined as well. From spectral analysis a new limitation has been derived for extension of some multiaxial cyclic fatigue criteria to random loadings. It is connected with the fact that in some cases the frequency band of the equivalent strain is greater than that for …

Analysis of Infrared and Raman-Spectra of 116SnH4 in the 1900 cm-1 Region - Study of the 1000, 0010 Interacting States

1991

0022-2852