Search results for "Frequency band"

A new Frequency Domain Measure of Causality based on Partial Spectral Decomposition of Autoregressive Processes and its Application to Cardiovascular…

2019

We present a new method to quantify in the frequency domain the strength of directed interactions between linear stochastic processes. This issue is traditionally addressed by the directed coherence (DC), a popular causality measure derived from the spectral representation of vector autoregressive (AR) processes. Here, to overcome intrinsic limitations of the DC when it needs to be objectively quantified within specific frequency bands, we propose an approach based on spectral decomposition, which allows to isolate oscillatory components related to the pole representation of the vector AR process in the Z-domain. Relating the causal and non-causal power content of these components we obtain…

2021

Previous work showed that the beginning of a sound is more important for the perception of loudness than later parts. When a short silent gap of sufficient duration is inserted into a sound, this primacy effect reoccurs in the second sound part after the gap. The present study investigates whether this temporal weighting occurs independently for different frequency bands. Sounds consisting of two bandpass noises were presented in four different conditions: (1) a simultaneous gap in both bands, (2) a gap in only the lower frequency band, (3) a gap in only the higher frequency band, or (4) no gap. In all conditions, the temporal loudness weights showed a primacy effect at sound onset. For the…

Optimum pulse shape for minimum spectral occupancy in FSK signals

1984

The characteristics of a frequency shift keying (FSK) signal giving rise to maximum power within a prescribed frequency band are determined. The baseband pulse shape extends over any integer number of bit periods. An integral equation for the optimum pulse shape is derived and some simple properties of the solution are investigated. The equation has been solved for some values of the product of the prescribed band times the pulse duration and the signal shape is shown. Our results for the particular case of pulses only one bit period long are presented for purpose of comparison with results known in the literature. Plots of out-of-band power for some values of the prescribed band and of pul…

A “Best Current Practice” for 3GPP-based cellular system security

2014

This paper is an attempt at formulating a Best Current Practice (BCP) for access security and a baseline for core network security in the 3GPP-based systems. This encompasses the 2G circuit-switched GSM system, the 2.5G packet-switched GPRS system, the 3G UMTS system and the 4G LTE/LTE-A system. The 3GPP have defined several security standards, but many measures are optional and there are several areas deliberately not covered by the 3GPP standards. The present document is therefore an attempt at pointing out the best available options and providing advice on how to achieve an overall system hardening, which is badly needed as the cellular systems have undoubtedly become one of the most cri…

Microtremor Measurements in the City of Palermo, Italy: Analysis of the Correlation between Local Geology and Damage

2008

Abstract This study presents the results of 90 seismic ambient noise measurements in Palermo, the main city of Sicily (Italy). The dataset has been processed using the horizontal-to-vertical spectral ratio (HVNSR) technique and interpreted in terms of local geology, which is characterized by the presence of alluvial sediments of two riverbeds masked by urbanization since the seventeenth century. HVNSRs show significant variations in the study area: when the transition stiff to soft is crossed, a typical spectral peak appears in the HVNSRs, mostly in the frequency band 1–2 Hz, and exceeding a factor of 3 in amplitude. Using available information on subsurface geological structure, we compute…

Analysis of duplexing modes in the IEEE 802.16 wireless system

2010

The IEEE 802.16 standard defines two main duplexing modes: Time Division Duplexing (TDD) and Frequency Division Duplexing (FDD). The FDD can be divided further into Full-FDD (F-FDD) and Half-FDD (H-FDD). F-FDD requires full duplexing support from subscriber stations and works with two frequency bands. TDD operates a single frequency band, but it does not need full-duplexing support. H-FDD is a combination of these: it works with two frequency bands and does not require full-duplexing support. The cost of this is a more complicated scheduling and added overhead. Still, H-FDD might be the only possible duplexing mode in some occasions. In this paper, these duplexing modes are compared and the…

Analysis of different Sleeve Ferrite Cores Performance according to their Dimensions

2019

Sleeve ferrite core is an EMI suppressor widely used to reduce the conductive and radiated electromagnetic noise in cables. The interconnection of different electronic systems through cables is becoming more difficult due to the hard restrictions related to EMC compliance requirements. Thereby, the research of new solutions able to provide a great attenuation ratio in a wide frequency band is a challenge. This contribution focuses on analyzing and comparing the performance of a novel sleeve ferrite solution based on a nanocrystalline (NC) structure with several materials with different compositions. This component is able to provide a high initial permeability value at the same time that ma…

Modeling and Experimental Verification of Ultrasound Transmission in Electro Insulation Oil

2012

A verification study of ultrasound transmission numerical simulation results with experiment results is presented in this paper. The work considers a model of a transformer tank which is filled with electro insulating oil. In the experiment, performed under laboratory conditions, an ultrasound wave is generated by a piezoelectric transducer that is fixed in the centre of the tank and measured by another transducer mounted inside the tank at three distances: 10, 20 and 30 cm from the sound source. The transducer is able to measure and generate acoustic waves in the ultrasound frequency band up to 1 MHz. The simulation considers numerical calculation of acoustic pressure distribution inside t…

Soot particle properties in the microwave range

1993

This paper outlines the study of Diesel soot particle properties in the frequency band 2.0-40.0 GHz. Using a transmission/reflection as well as a cavity perturbation method, the complex dielectric constant ?* = ?1 - j?2 was measured for multiple of samples (soot particles produced in a Diesel engine and deposited on paper filter). From the analysis of the experimental data the following conclusions appear: The complex dielectric constant - i.e. the HF electrical conductivity and the microwave power absorption efficiency - are dependent on the frequency and the soot particle thickness. Increasing the soot particle thickness causes the reflection to be stronger and results in less influence o…

Mechanical Coupling in Gold Nanoparticles Supermolecules Revealed by Plasmon-Enhanced Ultralow Frequency Raman Spectroscopy

2016

International audience; Acoustic vibrations of assemblies of gold nanoparticles were investigated using ultralow frequency micro-Raman scattering and finite element simulations. When exciting the assemblies resonantly with the surface plasmon resonance of electromagnetically coupled nano-particles, Raman spectra present an ultralow frequency band whose frequency lies below the lowest Raman active Lamb mode of single nanoparticles that was observed. This feature was ascribed to a Raman vibration mode of gold nanoparticle " supermolecules " , that is, nanoparticles mechanically coupled by surrounding polymer molecules. Its measured frequency is inversely proportional to the nanoparticle diame…