Main Source Of Interference Research Articles

Study of VLF Communication Technique Based on FRFT

The atmospheric noise generated by lightning phenomena is the main source of interference in VLF communications, it is rather difficult to detect the communication signal that not only merged in strong channel noise, but probably interfered by high-tension impulse caused by thunder. This paper, Alpha stable distribution noise model is proposed to simulate atmospheric noise firstly, then, we study a new technique of Chirp Spread Spectrum (CSS) communication based on Fractional Fourier Transform (FRFT), This paper studies a new VLF communication technique of the Chirp Spread Spectrum (CSS) communication based on Fractional Fourier Transform (FRFT), and it demodulates message utilizing energy gathering property of chirp signal in FRFT domain.

Simulation of VLF CSS System in Atmospheric Noise

Very Low Frequency (VLF) communication is designed to operate in the frequency between 3 kHz and 30 kHz. The atmospheric noise generated by lightning phenomena is the main source of interference in VLF communications, it is rather difficult to detect the communication signal that not only merged in strong channel noise, but probably interfered by high-tension impulse caused by thunder. This paper, Alpha stable distribution noise model is proposed to simulate atmospheric noise firstly, then, we study a new technique of Chirp Spread Spectrum (CSS) communication based on Fractional Fourier Transform (FRFT), This paper studies a new VLF communication technique of the Chirp Spread Spectrum (CSS) communication based on Fractional Fourier Transform (FRFT), and it demodulates message utilizing energy gathering property of chirp signal in FRFT domain.

Suppression measures for electromagnetic emission interference in low frequency range in hybrid electric vehicles

Limit–exceeding problems exist in electric field and magnetic field emission level in a type of hybrid electric vehicles. Characteristics of main electromagnetic interference source in the vehicles are analysed, production mechanism of radiated electric filed and magnetic field in the whole vehicle is discussed and the conclusion that the main interference sources of whole vehicle electromagnetic emission are three–phase working current of drive motor and electric motor controller is cleared up. Additionally, considering the properties of interference source, corresponding suppression measures for interference are proposed and applied. In the end, comparison validations with experiments are made to show that the whole vehicle electric field in low frequency range and the level of magnetic emission can be decreased by the suppression measures applied. The measures can also provide a reference for electromagnetic compatibility improvement in other hybrid electric vehicles.

Elemental analysis in environmental land samples by stand-off laser-induced breakdown spectroscopy

The stand-off detection and analysis of environmental land samples have been demonstrated using laser-induced breakdown spectrometry. The samples of interest have included soils and vegetation powder. Elements Hg, As, Pb, Zn, Cd and Cr have been spectrally analysed with a focus on Hg as a trace contaminant in the samples. It is found that element Fe, usually contained in land samples, is a main source of spectral interference for Hg detection due to its ever present iron emission line at 253.68 nm that is closely adjacent to the strongest Hg emission line at 253.65 nm, and hence, a high resolution of spectral detection is necessary. The strong spectral signals from Bremsstrahlung emission in laser-induced plasma and atomic emission of Fe of high concentration caused a significant reduction in detection resolution in the use of image intensifier of an ICCD. The limit of detection at ~8 ppm for Hg detection in soil samples with iron as a minor constituent has been achieved, using an optical chopper and a CCD detector for laser-induced breakdown spectroscopy (LIBS) signal detection. Such detection method in LIBS system has shown a great advantage in determining trace elements from interfering elemental constituents in land sample matrixes.

Reliable communication envelopes of molecular diffusion channels

Radio frequency communications are not always possible in hostile electromagnetic environments, and the molecular diffusion channel is considered as an information channel. A binary concentration modulated channel is considered and treated is the uncertain arrival time of particles as the main source of inter-symbol interference. The analysis derives the bit-error-rate and data rate expressions for a diffusion channel with zero drift. The minimum error rate and maximum data rate are derived analytically. It is also found that in order for reliable communications to be possible, the delay time must be greater than a threshold that is proportional to the square of the communication distance.

Research on the Electromagnetic Compatibility of Microcomputer Protection

This paper analyzed the main interference sources and their influences on the operation of protection both in the smart substation and the traditional substation. The interferences could be suppressed by reducing radiation of the interference sources, blocking the coupling channel of common-mode interference, promoting the anti-electromagnetic interference ability of the sensitive circuit and designing the bleeder circuit rationally. A microcomputer protection has passed the EMC test successfully by adopting these measures.

SYSTEMATIC ANALYSIS OF CONDUCTED ELECTROMAGNETIC INTERFERENCES FOR THE ELECTRIC DRIVE SYSTEM IN ELECTRIC VEHICLES

There are serious electromagnetic compatibility (EMC) problems in electric vehicles. In order to explain and solve them, a systematic method to analyze conducted interferences of the electric drive system is shown in this paper. This method represents the efiects of the power battery which is the most difierent part between electric drive systems used in electric vehicles and other cases. Also, equivalent models are established from power electronics devices to the entire system by considering both the working mechanism and stray parameters. Firstly, insulated gate bipolar transistor (IGBT) and inverter are studied as the main interference source. A new expression is put forward to estimate the frequency domain features of the inverter disturbances. Then, power battery and electric motor are discussed as the main propagation paths. Their high frequency circuit models are given with parameters obtained from tests and measurements. Finally, the system model is established. The system interferences are analyzed to get their generation causes, in∞uence factors and frequency domain characteristics. Comparisons between simulations and experiments verify the correctness of the models and the method.

Pièges et contraintes des dosages du calcium, des phosphates et du magnésium

Calcium, phosphate and magnesium are three current parameters of the “bone” laboratory tests. We describe the conditions of sampling, assaying, and discuss how to interpret these three parameters in the blood and urine. Total serum calcium remains the first-line setting. Correction in total serum calcium for albumin is justified only in cases of hypoalbuminaemia. Outside this context, a correction of serum calcium may mask diagnosis of hypercalcemia. The measurement of ionized calcium, non-automated, requires a rigorous preanalytical and can be reserved for some difficult situations. It eliminates the determination of serum albumin whose variability is important in case of inflammation. It allows a more sensitive diagnosis of moderate hypercalcemia. It ensures better monitoring of calcium status of patients with renal insufficiency. The presence of a monoclonal gammopathy is the main source of interference on the determination of phosphate, causing false hyperphosphatemia or rarely false hypophosphatemia. Serum magnesium, imperfect marker, remains the most accessible parameter for determining the status of magnesium in the body. Urinary assays are an integral part of the bone laboratory tests. The quality of the result depends on a prior acidification of the total urine volume considered.

Reducing Interference of Involuntary Movements in EEG Signal Analysis

Electroencephalogram (EEG) signal has conventionally been recorded with some devices, leads, an electrode cap, amplifier units, and A/D converters. The EEG signal can be contaminated by interference or sensor failures. Among the several artifact sources, an involuntary movement of patient is one of the main sources of interference in the EEG recording. The main objective of this study is to find the time of patient’s movement and to reduce noise effects from involuntary movements.

Time Domain Modeling of Powerline Impulsive Noise at Its Source

Noise characteristics of an indoor power line network strongly influence the link capability to achieve high data rates. The appliances shared with PLC modems in the same powerline network generate different types of noises, among them the impulsive noises are the main source of interference resulting in signal distortions and bit errors during data transmission. With regard to impulsive noise many models were proposed in the literature and shared the same impulsive noise definition: “unpredictable noises measured in the receiver side”. Authors are, consequently, confronted to model thousands of impulsive noises whose plurality would very likely come from the diversity of paths that the original impulsive noise took. In this paper, an innovative modelling approach is applied to impulsive noises which are studied here directly at their sources. Noise at receiver would be simply the noise model at source convolved by powerline channel block. In the new analytical model, the impulsive noise at source is described by a succession of short pulses, each modeled by a phase-shifted Gaussian. Noises at source are classified into 6 different classes [1], and a noise generator is established for each class.

Natural atmospheric noise statistics from VLF measurements in the eastern Mediterranean

[1] Very low frequency (VLF) (3–30 kHz) and extremely low frequency (ELF) (3–3000 Hz) electromagnetic transient signals and noise are generated by various natural and anthropogenic processes. On a global basis by far the most significant source is ELF/VLF radiation from lightning propagating in the Earth-ionosphere waveguide. This atmospheric “noise,” originating essentially from lightning discharges, is the main source of interference for VLF/LF telecommunications. One of the statistical measures that is used to define the properties of low-frequency radio noise is the voltage deviation Vd, which is a measure of the impulsiveness of the noise that is widely used to characterize radio noise, particularly in the International Radio Consultative Committee reports. In this paper we present atmospheric noise statistics based on VLF measurements at different temporal resolution (from minutes to seasonal variations). For the first time we present analysis of the statistical parameters of Vd from continuous broadband VLF measurements for a period extending more than 1 year. Our analysis shows that the long-term observed Vd characteristics can be reasonably estimated as the sum of two Gaussians distribution functions, while the hourly and seasonal distributions of Vd values can be fitted using a single Gaussian distribution with different mean and variance values.

Optical Coherent Receiver With a Switchable Electrical Dispersion Compensator for 10 Gb/s DPSK Transmission up to 300 km of SSMF in Metro Optical Networks

The purpose of this paper is to demonstrate the potential of an electrical signal processing technique to mitigate the effect of intersymbol interference in metro optical networks, using optical coherent detection. Intersymbol interference in fiber-optic systems can severely degrade the system performance and subsequently limit both the maximum transmission distance and data rate. The main sources of intersymbol interference include chromatic dispersion (CD) and polarization mode dispersion (PMD). The typical reach for 10 Gb/s metro optical systems is on the order of 300 km. To bridge this distance either with or without repeaters, we demonstrate the potential use of 10 Gb/s differential phase-shift keying (DPSK) modulation format in conjunction with an optical coherent receiver with a built-in switchable electrical dispersion compensator. The overall performance of the optical coherent receiver is compared with that of the corresponding direct detection (DD) receiver based on Mach-Zehnder delay interferometer. The optical signal-to-noise (OSNR) required to operate the optical coherent receiver at the enhanced forward error correction (EFEC) threshold of 2.1 X 10-3 is 6 dB/0.1 nm resolution bandwidth. The optical coherent receiver outperforms in absolute required OSNR by 0.5 dB at the EFEC threshold when compared to a DD receiver. A four position switchable CD compensator compensates up to ?5100 ps/nm of CD, using the method of heterodyne detection. The optical coherent receiver has a first-order PMD tolerance of 36.2 ps for 1 dB OSNR penalty. The utility of our optical coherent receiver is demonstrated by doing transmission experiments over 304 km of standard single-mode fiber (SSMF) in both repeatered (multiple spans) and repeaterless (single span) to measure the self-phase modulation (SPM) tolerance of 10 Gb/s nonreturn-to-zero (NRZ)-DPSK. The measured SPM tolerance of NRZ-DPSK over 304 km of SSMF in three spans of ~100 km each is +8.8 dBm fiber launch power for 1.5 dB OSNR penalty. In addition, the best Q factor of ~12 dB is obtained for the fiber launch power of +18 dBm over single repeaterless span of 304 km of SSMF, which gives ~3 dB of system margin at the second generation EFEC threshold of 9.1 dB.

Judicial Independence in China: Common Myths and Unfounded Assumptions

The Chinese judiciary is regularly criticized for lack of independence. The lack of genuine progress in establishing an independent judiciary is then cited as evidence that China's reform process is trapped in transition. In response, international donor agencies and bilateral legal cooperation programs have encouraged China to adopt institutions and practices found in advanced Western states known for rule of law. Surrounding these views is a set of common myths and unfounded assumptions. The first assumption is substantive: concept of judicial independence is clear, and there is a single agreed upon model or a generally accepted set of institutions and best practices articulated with sufficient specificity to guide reformers. The second assumption is methodological: there are clear standards for measuring judicial independence. The third assumption is normative: we know how independent courts should be (at each stage of development). The fourth assumption is more independence better. The fifth assumption is that lack of judicial independence is a serious problem in all types of cases in China. The sixth is that China's courts lack independence because independence is impossible within a single party state. The seventh, and a corollary, is that the Party is main source of interference with courts. The eighth is that were China to suddenly democratize, judicial independence would no longer be a problem. This article advances three main theses. First, each of these eight assumptions is either wrong or needs to be qualified. Second, general statements about lack of judicial independence or impossibility of achieving judicial independence in a single party state fail to capture complex reality of China or many other authoritarian regimes. Third, legal reforms that assign a high priority to judicial independence will be unsuccessful or limited in their effectiveness until there is a deeper understanding of these issues as they apply to China and to developing countries more generally. Part I distinguishes between various aspects or subcomponents of judicial independence. Part II then takes each of subcomponents of judicial independence in turn, reserving a discussion of main external constraints on judicial independence for Part III. Part IV discusses implications of China's efforts to increase judicial independence for law and development movement, including observations about methodology and relationship between regime type and judicial independence. Part V concludes with some recommendations on how to address related problems of judicial corruption and judicial independence.

The diagnostic research of telecom power converter with electromagnetic interference (EMI) suppressing technology

The main source of Electromagnetic Interference (EMI) emissions in power converters used for Telecom application comes from the high switching frequency of DC voltages. Power converters are generally operating in a periodic steady state, interested converter waveforms are typically periodic func- tions of time. Indeed the EMI emissions are a critical factor, which, can harm the system and degrade the satisfaction of Electromagnetic Compatibility (EMC). However, the most of design engineers use randomly various basic EMI reduction techniques. It is meaningful to quantify and analyze them before taking any solution measures. In fact, the diagnostic research of power converters is still under exploring. This article presents simplified equivalent circuit model used to predict the influence of common mode (CM) current noise in switching mode power supply. At the base of analysis, proposed equivalent circuit model contains essential couplings, parasitic elements, and sources occurred in the common mode current path. This cir- cuit composed of input cables; equivalent voltage source and the intentional parameters of the converter is examined theoretically. A comparative analysis between practical results and the proposed model highlight good matching. At last, effective EMI suppressing techniques has been realized on an AC/DC converter prototype in order to validate the proposed model.

A quantitative method for determination of Co(II) based on the inner filter effect of reagents on the Raman scattering signals of water

It is known that Raman scattering signals are one of main interference sources leading up to determination errors in spectrofluorometry, and thus the signals can be easily detected with a common spectrofluorometer. In this contribution, we propose a quantitative method based on the inner filter effect (IFE) of reagents on the Raman scattering signals of solvent by taking the complexation of divalent cobalt ion with 4-[(5-chloro-2-pyridyl)azo]-1,3-diaminobenzene (5-Cl-PADAB) as a model system. By adjusting the excitation wavelength of the spectrofluorometer, we could easily detect the Raman scattering signals of water at 424 nm where the maximum absorption of 5-Cl-PADAB reagent is located. In a solution of 5-Cl-PADAB, the Raman scattering signals of water are decreased owing to the IFE of 5-Cl-PADAB. If Co(II), which could form the binary complex of Co(II)/5-Cl-PADAB and consumes the 5-Cl-PADAB reagent, is present in such a case for a given amount of 5-Cl-PADAB solution, recovered Raman scattering signals could be observed and measured with a spectrofluorometer. It was found that the intensity of the enhanced Raman scattering signals is proportional to the Co(II) concentration over the range from 2.0 × 10 −7 mol L −1 to 1.0 × 10 −5 mol L −1, and the detection limit could reach 1.2 × 10 −7 mol L −1. With that, Co(II) in samples could be detected with R.S.D. values lower than 2.6% and recoveries over the range of 97.2–104.7%.

Modeling and simulation of unshielded and shielded energy cables in frequency and time domains

Switching of semiconductor devices is the main source of electromagnetic interference (EMI) in power static converters. Fast power devices, in particular, generate high levels of emissions in the form of high-frequency currents known as common mode (CM) and differential mode (DM) currents. In power systems, these high-frequency disturbances travel and spread over the power cables. To study the influence of the power cable characteristics on the level of the conducted emissions, it is necessary to construct a precise model of the power cables, taking into account various phenomena that appear when the frequency increases. This paper deals with two-wire unshielded and shielded energy cables. It uses a distributed parameter model that takes into account the skin and proximity effects, and the dielectric losses. The model is simulated and validated (with LT Spice/SwitcherCADIII software) in the frequency and time domains.

Ice Crystals and Raindrop Canting Angle Affecting the Interference Performance of a Double-Site Diversity Earth-Space System Employing Frequency Re-Use

In current satellite systems operating above 10 GHz the main sources of interference are the differential rain attenuation, as well as the rain cross-polarization (valid for frequency re-use systems). In addition, the ice crystals depolarization along with the raindrop canting angle effects may further degrade the carrier-to-interference ratio and this is more obvious for systems operating under the circular incident polarization. In the present paper, an existing method to predict the degradation of the (C/I) ratio due to all the above reasons, valid for single-site systems, is properly modified to include double-site interfered systems, employing frequency re-use. Another important point of the paper is the derivation of a set of simple regression formulas, appropriate for use by the system designer for back of the envelope computations. Finally, the difference between simulated results, derived after taking into account or not the ice crystals and raindrop canting angle effects, for various frequencies and polarization angles, is examined. Some useful conclusions are deduced.

On the Capacity Enhancement of a Cellular CDMA Channel with Asymmetrical Bandwidth Allocation

Capacity enhancement of cellular CDMA is analyzed using an asymmetrical-bandwidth-allocation approach. Cellular CDMA systems with and without successive interference cancellation are considered. The main source of interference is interuser interference and, in particular, a 9-cell configuration is employed to account for interference from surrounding cells. By transferring more bandwidth or, equivalently, processing gain from the forward link to the reverse link, we have effectively balanced their performance and raised the overall capacity of the cellular system. The optimum bandwidth allocation is easily obtained from the performance curves of both links. For a typical cellular CDMA with a bit error rate of 10^-3, the capacity gain of this approach is about 40%. If successive interference cancellation is employed and both links have the same quality, then both links should have equal bandwidth. However, in a situation where imperfect power control occurs, our studies indicate that using interference cancellation alone achieves a 25% increase in capacity, while enhancement with an asymmetrical bandwidth allocation overlay raises this gain to 68%.

Reduced order Kalman filtering for the enhancement of respiratory sounds.

In the processing and analysis of respiratory sounds, heart sounds present the main source of interference. This paper is concerned with the problem of cancellation of the heart sounds using a reduced-order Kalman filter (ROKF). To facilitate the estimation of the respiratory sounds, an autoregressive (AR) model is fitted to heart signal information present in the segments of the acquired signal which are free of respiratory sounds. The state-space equations necessary for the ROKF are then established considering the respiratory sound as a colored additive process in the observation equation. This scheme does not require a time alignment procedure as with the adaptive filtering-based schemes. The scheme is applied to several synthesized signals with different signal-to-interference ratios (SIR) and the results are presented.

A differential paramagnetic sensor for breath-by-breath oximetry

The operating principles of a fast paramagnetic oxygen sensor are described in detail. Some historical background of the paramagnetic effect in oxygen measurement is given as well. This sensor measures the difference between oxygen partial pressures in two gases as an alternating pressure signal being generated by the interaction of oxygen molecules with a switched magnetic field. Factors affecting the ideal performance of the sensor are analyzed. The main sources of interference are external pressure and vibration, and asymmetry in the transfer of the pressure signal to the microphone. Finally, the advantages of clinical breath-by-breath oximetry are briefly discussed.