Papers by Keyword: Low-Frequency Noise

Abstract: Substation noise pollution as one of the most important environmental problems has been paid more and more attention. A model of substation sound barrier is built in this paper. On the basis of the model, the effects of sound isolation of the barrier with different positions, different heights are analyzed. The setting of the sound barrier that can bring best sound insulation effect will be obtained from the simulation results. Moreover, as the substation control buildings can be seen as barriers, the analysis of the sound barrier attenuation can provide a certain basis for the layout of substation buildings, and the setting of noise reduction barriers for noise controlling.

Abstract: In allusion to the characteristic that transformer noise is mainly low-frequency noise, firstly the sound absorber is studied and analyzed on aspect of materials, sound absorption structure cavity thickness and punching rate etc in standing wave tube laboratory, secondly transformer substation low-frequency sound absorber is presented, and finally sound absorption properties of absorber is verified through random incidence Test. The analyses and study indicates that: compared with thin plate resonance absorber and micropunching sound absorber, the sound absorption band width of transformer substation low-frequency sound absorber has been improved under unchanged sound absorption effect and transformer low-frequency noise may be effectively absorbed.

Abstract: Low-frequency noise of the structures with Ge-nanoclusters of rather high surface density grown on the oxidized silicon surface is investigated for the first time. It was revealed that the 1/f ^γ noise, where γ is close to unity, is the typical noise component. Nevertheless, the 1/f ^γ noise sources were found to be distributed nonuniformly upon the oxidized silicon structure with Ge-nanoclusters. The noise features revealed were analyzed in the framework of widely used noise models. However, the models used appeared to be unsuitable to explain the noise behavior of the structures studied. The physical processes that should be allowed for to develop the appropriate noise model are discussed.

Abstract: Through the use of a spectral analysis of the source of noise – person’s movement over the ceiling construction – it was found out that in this kind of noise distinctive low-frequency tone components occur (31,5 - 40 Hz) which is beyond the evaluation area of the impact sound insulation of the ceiling construction, s. [2], [3].

Abstract: The paper discusses some issues connected to timber joist ceilings found not only in historical protected buildings but also in newly designed multi-storey timber based ones, with regards to their acoustic parameters perceived by the inhabitants of such objects. These problems are usually connected to the complaints of the users because of unsatisfying acoustic conditions indoors, observed mainly at low frequencies, even though the requirements given by the legislation are met. The paper with its content is a reaction to the contradiction between the results coming from measurements and subjective perception, and is complemented by structural evaluations seeking the effects of dynamic tremors and vibrations.

Abstract: Density of states in the channel bulk area of a-Si:H thin-film transistors (TFTs) was extracted by using low-frequency noise analysis. The drain current noise power spectral density shows 1/ƒγ behavior at relatively high frequencies (ƒ > 1 kHz), which is due to the exponential distribution of tail states. For the analysis, the modified number fluctuation model which is correlated with mobility fluctuation was used. From the relationship (γ=1- kT/Et ) between exponent γ and the slope of exponential distribution Et of band tail states, the distribution of the band tail near conduction band was extracted.

Abstract: A review of recent results concerning the low frequency noise in modern CMOS devices is given. The approaches such as the carrier number and the Hooge mobility fluctuations used for the analysis of the noise sources are illustrated through experimental data obtained on advanced CMOS generations. Furthermore, the impact on the electrical noise of the shrinking of CMOS devices in the deep submicron range is also shown.

Abstract: Microstructure and low-frequency noise test were measured for N80 steel casing drilling, through SEM analyzed their morphology. Results showed that: (1) power spectral density of 1/f noise increases two orders of magnitude after fatigue crack growth. (2) 1/f noise parameters of γ and B are significantly increased, indicating that the process of fatigue produced more cracks, defects, and combination centers, which were proved by microstructure morphology. From the mechanism of fatigue crack growth of N80, defects and cracks resulting from fatigue are the numbers of kind of fluctuations. In essence, low-frequency noise is a type of fluctuations, which can serve as a viable tool to study the defects and the characterization of defects.

Abstract: Low-frequency noise in 4H-SiC MOSFETs has been measured for the first time. At drain currents varying from deep subthreshold to strong inversion, the 1/f (flicker) noise dominated at frequencies 1 - 105 Hz. The dependence of relative spectral noise density, , on drain current Id (at a constant drain voltage Vd) differs qualitatively from that in Si MOSFETs. In Si MOSFETs, ~ 1/ in strong inversion, whereas tends to saturate in sub-threshold. In 4H-SiC MOSFETs under study, ~ 1/ over the whole range of currents from deep sub-threshold to strong inversion. Similar noise behavior is often observed in poly- or a-Si TFTs. The effective channel mobility in 4H-SiC MOSFETs, 3 - 7 cm2/Vs, is also as low as that in TFTs. Both noise behavior and transport properties of 4H-SiC MOSFETs are explained, analogously to TFTs, by a high density of localized states (bulk and interface) near the conduction band edge in the ion implanted p-well.

Abstract: An overview is given of analytical techniques for the characterization of the electrical and transport parameters in thin (<1 µm) semiconductor layers. Some of these methods have been applied to the lifetime and diffusion length study in thin strain-relaxed buffer (SRB) layers of strained silicon (SSi) substrates, while a second group was dedicated to Silicon-on-Insulator (SOI) materials and devices. The employed techniques can be divided into two groups, whether a device structure (junction, MOS capacitor, MOSFET) is required or not. However, the MicroWave Absorption (MWA) technique can be used in both cases, making it a versatile tool to study both grown-in and processing-induced electrically active defects. The transport properties of SSi wafers are strongly determined by the density of threading and misfit dislocations, although the dependence of the recombination lifetime is weaker than expected from simple Shockley-Read-Hall (SRH) theory. This is related to the high injection regime typically employed, enabling the characterization of the 250-350 nm thick Si1-xGex layer only. At longer carrier decay times, multiple trapping events dominate that can be described by a stretched exponent approach, typical of disordered materials. For SOI substrates, transistor-based techniques will be demonstrated that enable to assess the generation or recombination lifetime in the thin silicon film (<100 nm). The lifetime can be severely degraded by irradiation or hot-carrier degradation. Finally, it will be shown that Generation-Recombination (GR) noise spectroscopy as a function of temperature allows identifying residual ion-implantation-damage related deep levels, which are otherwise hard to detect even by Deep Level Transient Spectroscopy (DLTS).