On Impulsive Noise from Shinkansen

Measurements of impulsive noise radiating from individual bullet trains on the New Tokaido Line (called Shinkansen in Japanese) have been performed with the APD-CRD measuring apparatus using dipole antennas of vertical and horizontal types. Both an APD and a CRD have been simultaneously measured in a narrowband and at two frequencies of 50 and 100 MHz for noise samples taken in time succession for individual bullet trains. Based on the analysis of these measured APD's and CRD's, the following remarkable results have been obtained: APD's and CRD's, together with the parameters derived from individual APD's, average, rms, antilog of noise amplitudes, and the statistical parameter V0.1, can be grouped into three different environments of train speed and acceleration or deceleration. on. A model for the impulsive noise is presented, saying that any elementary section of overhead electric wire radiates impulses with amplitudes varying randomly during the time interval when it makes contact with pantographs on the top of vehicles. Good fits are shown between time variations of values of the statistical parameter V0.1 obtained as individual trains pass in front of the measuring site, and those of a certain related electric field calculated based on this model.     

Automotive Noise from a Motorway: Part I, Measurement

This paper describes 100-MHz measurements of the amplitude-probability (APD) and crossing-rate distributions (CRD) for automotive-traffic radio noise at Toyokawa, Japan. Two different categories of the results of measurements for automotive-traffic radio noise are described: 1) one category is the aggregate of APD/CRD pairs measured for the noise samples of 15-min duration, each of which gives a statistically stationary datum, and 2) the other is the aggregate of APD/CRD pairs measured for the noise samples of 2-s duration, each of which gives a transient datum belonging to the components of a statistically stationary datum. A series of the noise grades for single-motor vehicles passing on a motorway is described in terms of APD/CRD pairs for the noise samples of 2-s duration.     

Experimental Study of Pattern-Independent Phase Noise Accumulation in an All-Optical Clock Recovery Chain Based on Two-Section Gain-Coupled DFB Lasers

The pattern-independent phase noise accumulation in a chain of all-optical clock recovery devices (CRDs) based on two-section gain-coupled distributed feedback (TS-DFB) laser operating in the coherent mode is studied experimentally and theoretically. A simple theoretical model, where the CRD output phase noise is equal to the sum of the phase noise introduced by the CRD and the CRD input phase noise filtered by the phase noise transfer function, has been proposed for the CRD equivalent phase noise model. The accumulation of pattern-independent phase noise is investigated experimentally and theoretically for different cut-off frequencies of the phase noise transfer function of the TS-DFB laser and two different optical signal to noise ratios. It is shown that, due to the phase noise added by the CRD, phase noise accumulates in the passband of the phase noise transfer function, with the phase noise transfer function well approximated by a first-order lowpass filter. Excellent qualitative agreement between the experimental results and the theoretical model is observed. Also, it is concluded that the phase noise accumulation model for CRD, where the recovered clock is locked to the optical power of the incoming clock signal, presented by other authors holds in a qualitative point of view for the TS-DFB laser operating in the coherent mode. Since the root-mean-square (rms) of the timing jitter is proportional to the square root of the integrated power spectral density of the phase noise, the results show that a smaller cut-off frequency of the phase noise transfer function does not lead to a smaller rms value of the pattern-independent timing jitter along the chain of all-optical CRDs based on TS-DFB laser. It is shown that the minimum rms of the pattern-independent timing jitter along the CRD chain results from a compromise between the cut-off frequency of the phase noise transfer function and the phase noise introduced by the TS-DFB laser.     

Characterization of the modulation and noise properties of athree-electrode DFB laser

The modulation and noise properties of a three-electrode DFB laser have been measured. At proper biasing, the frequency modulation response could be chosen to be in phase or 180° out of phase with respect to the intensity modulation by selecting the modulated electrode. Applying a first order equalization/filter, a flat frequency modulation response was measured up to 5 GHz. A 20-dB broadband suppression of the intensity modulation was accomplished when modulating two sections in push-pull. The spectral densities of the FM and intermodulation noise were measured showing remarkably flat intermodulation and FM noise spectra     

汉语语言谱窄带噪声向上掩蔽特性的测量

以汉语语音清晰度客观评价方法为背景,对汉语语言谱噪声相邻倍频带间的向上掩蔽特性进行了实验测量,与语言传输指数(STI)算法中采用的低频窄带噪声向上掩蔽模式的结果进行了对比分析。实验结果表明,当掩蔽声的声压级固定时,掩蔽斜率会根据掩蔽声频率的不同而有所不同但差别较小;当掩蔽声的频率一定时,随着声压级的提高,掩蔽斜率是渐增的趋势但并不明显,掩蔽斜率值基本保持在30~35 d B/octave之间,这与STI算法中使用掩蔽量级有较大的不同。     

三维枪弹痕点云数据处理及特征提取研究

为了解决传统算法中弹痕图像深度特征信息丢失的问题，本文提出一种能够计算出弹痕图像深度特征参数信息的三维点云图像特征提取算法。该方法根据棱线斜率变化从局部极值点中找到特征点，运用线性拟合法构建三角形对特征参数值进行计算，确定弹痕特征参数值的相似范围，通过利用相似范围对未知弹头进行判别，实现弹痕和枪的一致性确认。实验结果表明：所提出的算法在现有样本的条件下，弹痕比对的正确识别率达到90%以上，单组弹痕数据的转换、特征提取和参数计算共用时32.7 s。算法满足弹痕比对需求，可以对后续弹痕比对提供可信依据，具有一定的理论价值和实用意义。     

网络瓶颈带宽测量的噪声分析

包对/串技术通过两个/多个背靠背发送的测量包所经历的散布间隔来估测一条路径的瓶颈带宽.本文分析了瓶颈带宽测量中的噪声特性,解释了在不同测量包长和测量包数情况下测量样点的分布.基于噪声分析的结论,文中提出了一种基于信号模式的滤波算法(MBFA,Model-Based Filtering Algorithm),它利用信号模式/特征来增强信号、过滤噪声.     

Anomalous CV curves of Al/SRO/Si structure after electrical stress

The electronic transport property of silicon-rich oxide (SRO) films under electrical stress was studied in Al/SRO/Si structures using capacitance versus voltage (C–V) and current versus voltage (I–V) measurements. The measured C–V curves show an unexpected vertical shift either upward or downward. Analysis of the data shows that these upward and downward shifts can be almost totally attributed to a sudden change of the capacitance of the SRO layer. I–V measurements also present some abrupt jumps in current. A simple model was proposed to explain the experimental results taking into account the change of the transport properties of the SRO layer. It is proposed that under electrical stress the SRO film can be switched between two states: low resistive and high resistive states. These conductive states are produced by the creation and, or annihilation of neutral traps, or defects, in the SRO layer. If defects are created, they will “connect” adjacent excess Si dots already existing in the material, then percolation paths would be formed and electrons could move through these paths resulting in a low resistive state. On the other hand, if the defects are annihilated by electrical stress, the percolation paths would be eliminated and the SRO layer turns to a high resistive state. Then, the switching between the on and off states of the SRO films under electrical stress would produce the anomalous shifts observed in the measured C–V and I–V curves.     

Berechnungsmethoden zur Ermittlung der Schutzstrecke bei U- und Stadtbahnen

One essential component of project planning of train control system plants is the design and calculation of the protective route. At first, definitions of the most important terms are explained. There are three different calculation methods depending on the regard of the slope of the track system as well as on the train mass representable. The simplest method only considers the maximum slope before the signal and the danger point. The second method considers the slope of the track in the form of stairs. The gradient method is presented as a third method. The regard of the inclination gradient occurs here in the form of a twofold averaging. On the one hand the mean value in the form of an integral is formed via the train length. On the other hand averaging occurs in the form of an integral via the braking distance. The middle inclination value found in this way is inserted in the iterative process for the determination of the protective route.     

Trap characterization in buried-gate n-channel 6H-SiC JFETs

We present a detailed characterization of deep traps present in buried gate, n-channel 6H-SiC JFETs, based on transconductance measurements as a function of frequency. Four different deep levels have been identified, which are characterized by activation energies of 0.16, 0.18, 0.28, and 0.54 eV. Furthermore, based on the transconductance frequency dispersion features (upward or downward dispersion), we have been able to infer that three deep levels (0.16, 0.18 and 0.54 eV) are hole traps localized in the p-gate layer and one (0.28 eV) is an electron trap localized in the n-channel     

Soft-error-immune switched-load-resistor memory cell

A soft-error-immune switched-load-resistor memory cell especially suitable for ultrahigh-speed bipolar RAM has been developed. The memory cell is composed of upward sidewall base contact structure (SICOS) transistors and shielded Schottky-barrier diodes (SBDs). Alpha-particle-induced noise charges generated in the p^--substrate are completely shielded by n⁺-buried layers of the transistors and the SBDs. Only the noise charges generated in the transistors or the SBDs active regions are gathered in the collectors of the memory cell. The maximum collected noise charge is reduced to a quarter of that of conventional memory cells using SICOS downward transistors and conventional SBDs. Experiments show that this reduction of the collected noise charge increases soft-error immunity to more than 10⁵ times that of conventional memory cells. This result using hot radiation sources does not directly correspond to the real soft-error rate in the field, but demonstrates the realization of an ultrahigh-speed soft-error-immune memory cell     

QRS slopes for detection and characterization of myocardial ischemia.

In this study, the upward I(US) and downward I(DS) slopes of the QRS complex are proposed as indices for quantifying ischemia-induced electrocardiogram (ECG) changes. Using ECG recordings acquired before and during percutaneous transluminal coronary angioplasty (PTCA), it is found that the QRS slopes are considerably less steep during artery occlusion, in particular for I(DS). With respect to ischemia detection, the slope indices outperform the often used high-frequency index (defined as the root mean square (rms) of the bandpass-filtered QRS signal for the frequency band 150-250 Hz) as the mean relative factors of change are much larger for I(US) and I(DS) than for the high-frequency index (6.9 and 7.3 versus 3.7). The superior performance of the slope indices is equally valid when other frequency bands of the high-frequency index are investigated (the optimum one is found to be 125-175 Hz). Employing a simulation model in which the slopes of a template QRS are altered by different techniques, it is found that the slope changes observed during PTCA are mostly due to a widening of the QRS complex or a decrease of its amplitudes, but not a reduction of its high-frequency content or a combination of this and the previous effects. It is concluded that QRS slope information can be used as an adjunct to the conventional ST segment analysis in the monitoring of myocardial ischemia.     

Advanced Communications Satellite Systems

Demand for in-orbit capacity through the use of satellite systems will continue throughout the next two decades. The potential of the 30/20 GHz frequency band for fixed satellite services will be exploited. However, many technology questions must be answered if the band is to be used commercially because of the high rain fades that can occur at these high frequencies. NASA has conducted a technology development program in high gain antenna and on-board switching and processing systems which can be combined such that cost competitive services are possible at acceptable rain outage percentages. Other supporting technologies have also been pursued including transmitters, both tube type and solid state, and low noise receivers. The critical technologies have been combined into an experimental satellite payload; an experimental flight is planned to verify these technologies and enable development of operational systems. Implementation of such systems would be by commercial carriers and could occur in the early 1990's, depending on the demand for additional or bit capacity. The high capacity systems that can be made possible through the use of the 30/20 GHz band and the employment of frequency reuse technology will contribute to the continued downward trend in circuit costs and may allow new and innovative satellite services.     

Impulsive noise measurements and characterization in a UHF digitalTV channel

This paper presents the results of a study covering measurement and characterization of the wide-band impulsive noise present in a digital TV radio channel. Measurements were conducted at a frequency of 762 MHz in different outdoor and indoor environments using vertical and horizontal polarization. The measurement system was built on commercial equipment only. The calibration process, which is an important stage of this kind of measurements, is described. To analyze the measurements the impulsive noise has been modeled as a pulse train where the pulse amplitude, pulse duration and elapsed time between pulses are considered random variables. It has been found that the pulse duration and elapsed time between pulses is not dependent on the antenna polarization while the pulse amplitude is, especially in the case of the noise generated by a fluorescent lamp. It has also been found that the pulse duration of the noise measured in the outdoor environments presents some clustering features and is correlated with the pulse amplitudes. This correlation may be caused by a RF noise bandwidth that is larger than the bandwidth of the measurement system. The noise in busy streets presents larger pulse durations, larger amplitude, and shorter elapsed time between pulses that the noise measured in a pedestrian area. Several statistical tests have been done to find the distribution function that best fits these random variables. Power Rayleigh, lognormal, exponential, Poisson, and Gamma distributions have been tested. According to the assessment carried out, none of the distribution functions is adequate to model the pulse amplitudes or the elapsed time between pulses, while the pulse duration seems to be Gamma distributed     

Local Piezoelectricity and Polarity Distribution of Preferred <Emphasis Type="Italic">c</Emphasis>-Axis-Oriented ZnO Film Investigated by Piezoresponse Force Microscopy

The piezoelectric properties and polarity distribution of preferred c-axis-oriented ZnO films have been investigated using piezoresponse force microscopy (PFM). Simultaneous imaging of the morphology, as well as the magnitude and phase of the out-of-plane and in-plane piezoresponse, was performed by PFM on the ZnO films. The out-of-plane piezoresponse with two primary antiparallel spontaneous polarization orientations (upward and downward), which is perpendicular to the surface of the film, has been found, and the spontaneous polarization orientation of most grains is upward. Meanwhile, the in-plane piezoresponse has also been detected in some of the grains. In addition, the polarization orientation of the individual grains is discussed and determined by analyzing phase images of the out-of-plane and in-plane piezoresponse.     

AM and FM Noise of BARITT Oscillators

AM, FM, and baseband noise of a BARITT diode oscillator in the range 100 Hz-50 kHz off the carrier has been measured under various operating conditions. A simple calculation has been made, relating the baseband noise to the oscillator AM and FM noise via measured amplitude and frequency modulation sensitivities and the results have been compared with the noise measured. It is shown that, depending on the bias current applied, both AM and FM noise performance can be degraded by up-conversion. Complete removal of up-converted noise requires a high-impedance low-noise bias supply since both the diode noise and bias supply noise at baseband frequencies may be significant when up-converted. Even with all modulation suppressed, the AM and FM noise has a flicker component almost completely correlated with the diode flicker noise at baseband frequencies. The RF power dependence of the AM and FM noise has also been investigated. It is shown that the BARITT oscillator noise compares very favorably with that of IMPATT's and TEO's. Values of -142 dB/100 Hz (AM noise) and 3.5 Hz/(100 Hz)/sup 1/2/ for Q/sub ext/ = 200 (FM noise) have been measured at 30 kHz off the carrier.     

GPS全自动公交语音报站器的研究

针对国内系统报站装置应用的现状．提出一个基于GPS全球定位的公交全自动报站系统。该装置公交采用MCS-51单片机及GPS定位技术．利用GPS模块测得的经纬度信息与存储在单片机中的站点的经纬度信息相比对,无论上行线路,还是下行线路,均能准确判断是否到站。同时,采用基于文本的语音合成技术,真正实现了全自动、准确地播报站名及服务提示信息。     

BP神经网络预测算法性能的改进策略

预测可以为系统的正常运行提供良好的保障.依据BP神经网络预测算法的特性及电信网络的特点,提出了通过加入周期算法、数据整体上移或下移的预处理来提高预测性能的策略.并对此两种改进策略进行了试验论证.     

Sensitivity measurements of a passive intermodulation near-field scanner

A passive intermodulation (PIM) near-field XY scanner for the GSM900 frequency band has been constructed to localize distortion sources in antennas and in other open structures. The equipment should be able to measure distortion levels down to -115 dBm with an input power of 2/spl times/20 W, since the noise floor of a GSM900 base station is typically around -110 dBm. The sensitivity is limited either by thermal noise or by residual intermodulation distortion, depending on the probe coupling. Various causes of residual intermodulation distortion in the passive intermodulation near-field measurement are considered and evaluated. Sensitivity measurements of the scanner have been carried out on two test devices. Sensitivities of -112 dBm and -110 dBm have been achieved with an electric and a magnetic field probe, respectively.     

Comb-like profiled fibre for efficient generation of high quality 160 GHz sub-picosecond soliton train

A comb-like profiled fibre (CPF), an alternate concatenation of a dispersive fibre and nonlinear fibre, is capable of emulating an arbitrary dispersion profile over distance for high quality optical pulse compression. It is demonstrated experimentally that CPF is efficient for the reshaping of an optical beat signal into a high quality 160 GHz 730 fs soliton pulse train with remarkably low noise, while stimulated Brillouin scattering was well suppressed.