1,721,134 research outputs found
1/f NOISE IN LARGE SIGNAL OPERATION OF PASSIVE COMPONENTS
No full textA model for the 1/f noise in large signal operation of linear passive one-port (e.g. carbon or polysilicon resistors) is given. Starting from the Hooge's formula, that holds when the component is operated under DC bias, it is shown that the noise current is simply proportional to the product between the conductivity fluctuation and the time-dependent large signal applied to the component. Otherwise stated, the 1/f noise exhibited by passive components in large signal operation arises from the intermodulation between the stochastic process "conductivity fluctuation" and the signal applied to the component. Detailed calculations of both autocorrelation function and power spectrum of the resulting noise current are given; different time dependence of the signal applied to the component are considered. Of particular relevance in practical applications is the case of sinusoidal signal plus an eventual DC bias; in this case the resulting noise current is a cyclostationary stochastic process, and its behaviour can be conveniently described by the cyclic autocorrelation functions or by the cyclic power spectra. The measured power spectra of the noise current of carbon resistors with DC bias and large periodic signal applied to them, are in good agreement with those calculated from the proposed model. The agreement of the measured power spectra with those predicted by the model allows to conclude that the physical origin of 1/f noise in passive components does not depend on the applied bias, DC or large signal alternating, since, in any case, the noise current is conveniently modeled by intermodulation (product) between the "conductivity fluctuation" stochastic process and the applied signal
Analysis of a Single-mode Optical Fibre Piezoceramic Phase Modulator
No full textThe behaviour of a cylindrical single-mode optical fibre piezoceramic phase modulator was investigated in the frequency range below resonance. The integral and differential phase modulation efficiencies are reported for different geometrical dimensions of the modulator and for various piezoelectric ceramic materials. The results obtained show that a phase-modulation depth in excess of 180deg can be easily achieved using commercially available piezoelectric cylinders, with driving voltage amplitude as low as 5 V
Bend Loss in Single-Mode Fibers
No full textIn this paper, we present the results of extensive single-radius bend loss measurements for two different fibers over wide ranges of wavelength (800-1600 nm) and curvature radius (13.5-27.5 mm). A new bend loss formula is also derived, allowing a good fit of experimental data over the whole range of both parameters. Using an equivalent step-index (ESI) approach we obtain a good agreement between estimated and real parameters: e.g., cutoff wavelengths are within 1
Design criteria for pixel-level integration of optical rangefinders in 3-D pickup device
No full textDesign issue and criteria are discussed for a Time-of-Flight based, 3D image pick-up system, and some experimental results are shown
Recovery of Noise-Corrupted NMR Data acquired and accumulated in unstable Magnetic Field
No full textDuring Acquisition of NMR signals in unstable magnetic field and low Signal to Noise Ratio, a typical error appears, arising from noise rectification. Results of the application of a previously presented technique for noise error compensation are shown, with reference to T1 and T2 estimation. Signals are acquired by a new equipment, using Fast Field Cycling
Noise in VCO and PLL - Noise figure control in LNA
No full textNoise in VCO and PLL:
Noise properties of VCO and PLL, key components of modern telecommunication systems, have
been studied. Noise due to internal white noise sources in steady-state oscillators is well described
by random walk phase noise, that causes zero-crossing jitter, plus amplitude noise, that is usually
negligible in applications. In VCO, the control voltage does a®ect not only the frequency, but noise
sources too; starting from this observation, accounting for the intermodulation between control
signal and noise sources, a model for phase noise in VCO when a time varying control signal is
applied has been developed and tested with simulations. Preliminary results regarding square wave
modulation are available for now.
Noise figure control in LNA:
Continued in 2005 the cooperation with the RF Group on the study of noise ̄gure control techniques
in LNA, mainly for cellular phones and portable terminals. In the context of re-con ̄gurable
multistandard, multi-frequency applications, the portable terminal should adapt itself, in addition
to changes in the frequency band of operation, to other time-varying RF environmental conditions,
such as signal strength and blockers strength. Aiming at power consumption reduction, the frontend,
and the LNA in particular, should not be designed to operate always at minimum noise ̄gure,
since noise ̄gure is almost always reduced at the cost of higher power consumption. Signi ̄cant
power saving can be achieved by allowing noise ̄gure to rise, without a®ecting the quality of the
received information, when certain signal strength and blockers strength combinations are met, e.g.
strong signal and weak blockers. Publication of the results is expected in 2006
Noise figure control in LNA - Low-frequency noise reduction in Operational Amplifiers
No full texti - Noise figure control in LNA
Noise figure reduction in LNA for portable terminals and cellular phones have been investigated
in cooperation with the RF group. In demanding applications, such as re-configurable, multistandard,
multi-frequency, the portable terminal should optimize its performances by adapting the
power consuption and noise figure to the different operating conditions in a time-varying environment.
Aiming at longer battery life, maximum signal-to-noise ratio operation is not always the best
choice. In presence of strong signal and weak blockers, signal-to-noise ratio can be lowered without
sacrifying the received information quality, with the advantage of a lower power consumption and
longer battery life. The common gate LNA has been deeply investigated, giving a unified description
of all feedback configurations, providing analytical expressions for gain, noise and linearity
for bipolar and CMOS technology. The flexibility of these structures has suggested a novel design
methodology oriented to configurable low noise amplifiers both in frequency and in performance.
ii - Low-frequency noise reduction in Operational Amplifiers
The limits of the conventional chopper stabilization technique for cancelling the 1/f noise has
been studied theoretically and with simulations, in cooperation with the Microsystems group. The
expected replicas of the 1/f noise at the chopping frequency and its multiples are attenuated by a
modified chopping control, based on the use of a square wave clock with a large amount of phase
jitter, i.e. with a large linewidth. Simulation done using records of real 1/f noise outputs has shown
that the spectrum of the signal is not modified, while 1/f noise replicas are reduced by more than
40 dB. The required circuit for the generation of the chopping signal has been described too; the
resulting overhead with respect to conventional techniques is negligible and fully acceptable
Identità narrativa e identità traduttiva: due possibili paradigmi per la psicoanalisi?
No full textThe Authors discuss the question of narration and narrative identity starting from the work of Paul Ricœur and illustrate the reception and the application of narration in the psychoanalytic field. Their reflection proceeds towards an enhancement of the third paradigm of Ricœurian hermeneutics: the translation, of which the Autors discuss the possible strengths in a philosophical and psychoanalytic field. A comparison is thus proposed between the interpretation, narration and translation, always referred to psychoanalysis
- …
