查询词典 signal to noise ratio

At first, setting up the arith relation between the signal input and the signal output of the generalized multi-carrier system of the Discrete Fourier Test spread-spectrum; then setting equilibria parameters of the frequency field equilibria subcarrier of the generalized multi-carrier system of the DFT spread-spectrum according to channel frequency response, channel noise variance and equilibria method; then calculating average power of useful signal, interferential average power between signals as well as noise variance of the generalized multi-carrier system receiving terminal of the DFT spread-spectrum according to the arith relation as well as the frequency field equilibria parameter, and recomputing available signal information noise ratio, so as to calculate the available signal information noise ratio of the generalized multi-carrier transmission system accurately, the method for estimating the available signal information noise ratio can be used for link self-adapting transmission solution of the generalized multi-carrier system based on Discrete Fourier Test spread-spectrum and radio material management.

一种DFT扩频的广义多载波系统的SINR估计方法，其通过首先建立所述离散傅立叶变换扩频的广义多载波传输系统的信号输入输出之间的数学关系，然后根据信道频率响应、信道噪声方差和均衡方法，设定所述DFT扩频的广义多载波传输系统的频域均衡子载波的均衡系数，再根据所述数学关系及所述频域均衡系数分别计算所述DFT扩频的广义多载波传输系统接收端有用信号的平均功率、信号间干扰的平均功率以及噪声方差，再计算有效信干噪比，如此以实现对广义多载波传输系统的有效信干噪比的准确计算，该有效信干噪比估计方法可用于基于离散傅立叶变换扩频的广义多载波传输系统的链路自适应传输方案和无线资源管理方面。

When the mind apprehends the essence of a thing (quod quid est; tò tí en enai), the external object is perceived without the particular notes which attach to it in nature, and it is not yet marked with the attribute of generality which reflection will bestow on it.

当铭记apprehends的本质的东西（狱吏嚼1-5 ；德州仪器恩enai ），外部对象被认为没有特别注意到它重视它的性质（中存在singularibus ），这是没有标明属性一般性的反映将赋予它

The main job and contribution of this paper are as follows:Based on narrowband signal processing, we propose a new method for FH signal blind detection and blind parameter estimation. Firstly, compute the cross-correlation function of FH signals from multichannels, then we get the cross power spectral density matrixCSDM Secondly, select the hops of FH signals from the CSDM via processing and analyzing the CSDM, meanwhile reduce the influence coming from noise, fixed frequency signal and other interferences; Lastly, estimating the DOA of every hop and according to the DOA, we can separate the hops, get the number of FH signals and their parameters. Propose a new method for designing the threshold in FH signal detection. This method makes it easy to get the threshold by theoretic computing and it can extremely reduce the interference of non-FH signals.Based on broadband signal processing, we propose a new method for FH signal blind detection and blind parameter estimation. Firstly, get the DOA of the signals by wideband spatial spectrum estimation; secondly, separate the signals by spatial filtering using wideband beamformer; Lastly, we propose two methods for FH signal blind detection and blind parameter estimation, one is for several constant hop-rate FH signals whose dwell-time are different and another is for a single FH signal whose hop-rate is alterable.By employing spatial interpolation in broadband signal beamforming, it can reduce the number of antenna elements and corresponding RF modules, A/D converters, etc. It can also eliminate the mutual coupling between antenna elements while getting the narrower main beamwidth and lower sidelobe level.

本文的主要研究工作和贡献如下：●提出了一种基于窄带处理的FH信号盲检测和参数盲估计的实现方法，即首先求出多路信号之间的互相关，进而得到互功率谱密度矩阵，然后通过对CSDM进行对折处理来抑制噪声、定频信号及其他干扰的影响，并将所有属于FH信号的hop(每一跳的驻留时间在时频图上持续的线段)从CSDM中筛选出来，最后用阵列信号处理中的到达方向估计理论在频域中估计出各个hop的方向参数，利用方位信息完成FH信号分离并得到FH信号的数目及其各自的参数集；●提出了一种确定FH信号检测门限的策略，该策略不仅使得检测门限能够通过理论计算得到，而且还显著地抑制了非跳频信号的干扰，从而能有效地检测出FH信号；●提出了一种基于宽带处理的短波FH信号盲检测和参数盲估计的实现方法，即首先利用宽带空间谱测向技术得到接收信号的DOA，然后采用宽带波束形成技术对特定方向进行空间滤波，实现多个信号的分离，最后分别提出了两种FH信号的盲检测和参数盲估计方法，第一种方法适用于空间某个特定方向上存在着几个驻留时间不同的恒跳速FH信号和其他干扰信号的混合信号，第二种方法适用于空间某个特定方向上仅含一个可变跳速的FH信号和噪声的混合信号；●将空间插值的概念和宽带波束形成技术结合起来，提出了一种基于频域处理的宽带恒定束宽的波束形成方法。

To estimate the high signal to noise ratio in every recorded trace using quantitative method and erase the recorded traces with low signal to noise ratio so as to form a standard trace with high signal to noise ratio.

在形成标准道时，利用定量估计信噪比的方法，对每个记录道分段进行信噪比估计，剔除信噪比低的记录段从而形成高信噪比的标准道。

Noise can be reduced by about 2 dB by using oil-resistant rubber isolator to reduce solid-borne sound transmission; the setting-up of semienclosed noise barriers can not only reduce the work region's noise of workshop by 13 dB, but also adapt to the gas's characteristic involved with H2S, CO, and other poisonous components without supplied mandatory ventilation; locating the noise absorbers on the walls and ceiling of workshop can reduce noise by 8 dB; the exhaust silencer's elimination volume can reach above 30 dB which is designed in accordance with the exhaust noise spectrum characteristic of gas-combustion generator. By the combination of these measures, the noise of the gas- combustion generator will be under effective control, so that the gas power plant's noise pollution problems can be resolved.

通过选用耐油性好的橡胶隔振器减少固体传声，可降低噪声约2 dB；设置半封闭式机组隔声屏障可降低生产车间工作区域内的噪声达13 dB，并且适合瓦斯发电气源中含有H2S、CO等有毒有害气体的特点，不需增加强制通风措施；在生产车间四周墙壁和顶棚上敷设吸声体，最大可降低空间噪声8 dB；根据瓦斯发电机排烟噪声频谱特性设计的阻抗复合式消音器的消音量可以达到30 dB以上。

Based on a series of signal process and noise source identification techniques, especially the major noise source identification methods, such as expurgation method, sound intensity analysis, spectrum analysis vibro-acoustic correlation analysis and so on, the pass-by noise control of SC7080A and SC6360B are studied in detail. By the roadway and dais experiments, the major noise and radiating parts are identified and some economical controlling methods are made. For the SC7080A, to control the emissing noise from the intake and shell vibration of air cleaner, a intake muffler is installed between the air cleaner and intake valve. Based on the theory of Helmholtz resonator, One three-parallel-connected resonant silencer is designed and trial-manufactured. For the SC6360B, the attenuation performance of exhaust muffler in high frequency region is improved. To reduce the vibration noise of shell part, the structure of oil sump tank, exhaust manifold shield and exhaust manifold shield are analyzed and improved. At the same time, some measures, such as sound absorption, sound insulation, are taken to reduce the noise of engine surface emissivity and a sound shield is designed.

本文首先综述了目前国内外汽车加速噪声控制的现状、主要方法和技术措施，在此基础上，结合SC7080A和SC6350B汽车的车外加速噪声水平及现状，综合运用分别运行法、声强法、频谱分析法、声振相干函数法等现代噪声源识别方法，对SC7080A和SC6360B汽车进行了准确详细的车外加速噪声源识别并提出了经济可行的控制方案，针对SC7080A，主要在空气滤清器和进气阀门之间的进气管道上加装进气消声器，抑制空气滤清器壳体表面和进气口两处的噪声辐射，根据Helmholtz共振腔原理设计了三腔并联旁支型共振消声器，并进行了工程化设计和试制；针对SC6360B，主要改善了排气消声器在高频段的消声性能，对罩壳类零件进行了结构改进，降低了其表面噪声的辐射，并对发动机舱进行了吸声、隔声处理，设计了发动机隔声罩。

For the problem that the suppression of co-channel interference and suppression of noise can't be balanced in signal-to-jamming and noise ratio maximization method for the linear precoding of multiuser multiple-input multiple-output downlink systems, an improved scheme that the term of noise variance is modified as a piecewise linear function is proposed, in which the balance between suppression of co-channel interference and suppression of noise can still be maintained even when the noise variance is a small value through piecewise modifying the term of noise variance, and thus the bit error rate and capacity of the systems are further improved.

针对多用户多输入多输出系统下行链路线性预编码的信干噪比最大化方法中，共信道干扰抑制和噪声抑制不能有效平衡的问题，提出将其中的噪声方差项修正为以噪声方差为变量的分段线性函数的改进方案。该方案通过对噪声方差项的分段修正，在噪声方差的值较小时依然能够保持共信道干扰抑制和噪声抑制间的平衡，从而使系统的误比特率性能和容量得到进一步提高。

First, the effects of magnetic RAM relaxation time and the rise-time of incident pulse signal on reflection signal are discussed, the relationship between the rise-time of incident pulse and relaxation time based on the energy of reflection signal is revealed. Then, the effects of magnetic hysteric, susceptibilities and saturation upon reflection signal are analyzed, the results reveal the reflection of RAM target and UWB signal design. In the meantime, dielectric relaxation time effect about dielectric RAM target is analyzed simply, and the effects of relaxation time and the width of incident pulse upon reflection signal are probed. Finally, a few RAM targets are measured in the chamber using the impulse radar experiment system which is developed by the team of anti-stealth impulse radar on Department of Electrical Engineering, National University of Defense Technology. The experimental results show the similarity of the rule of echos with the theory. From the compared results of different tagets, we concluded, compared with 15% wideband sinusoidal signal, the impulse signal has increased 10～12dB energy from the same loaded RAM target; this, in turn, shows the nonlinear effects of RAM to the echoes, and the potentiality of the impulse signal to RAM targets.

首先分析了磁性RAM的弛豫时间及入射脉冲信号的上升时间对反射信号的影响，从反射信号能量角度出发，给出了入射脉冲上升时间与弛豫时间的关系；接着分析了磁性RAM的磁滞特性、磁化率及磁化强度对反射信号的影响，给出了RAM目标辐射和有关UWB信号设计的一般性结论；其次，对介电RAM的弛豫时间效应作了简单的分析，探讨了介电弛豫时间及入射脉冲宽度对反射信号的影响；最后利用国防科技大学电子技术系&反隐身冲激雷达技术研究组&研制的冲激雷达实验系统，在微波暗室中对几种不同的RAM目标进行了测量，结果表明：其反射波形的基本规律与上述理论分析相一致；从各种不同目标回波的能量对比结果得出，涂覆RAM目标对冲激信号的吸收比15％带宽的正弦信号要小10～12dB，证实了RAM的非线性效应对回波的影响，也证实了冲激信号反隐身的潜力。

Studied the solid particles cyclone separation under structural parameters and operating parameters of different hydrocyclone, the results showed that major factor influence split ratio is in the ratio of entrance to exit pressure of hydrocyclone. Exit pressure has a certain influence on the split ratio, the various of the diameter and cone angle of hydrocyclone (in the ratio of entrance to exit pressure is constant) have no influence on split ratio; With diameter and cone angle increase, the separation granularity gradually increasing and recovery ratio decreasing; With entrance pressure increase, the separation granularity of hydrocyclone decrease, the split ratio of underset will increase slowly; With the diameter of overflow pipe increase, the separation granularity of hydrocyclone increasing and recovery ratio decreasing; With the diameter of underset pipe increasing, the separation granularity of hydrocyclone decreasing and recovery ratio increasing.

在不同的水力旋流器结构参数和操作参数下，对固体颗粒的旋流分离进行了分析研究，结果表明：旋流器的排出口比是影响分流比的主要因素，进口压力对分流比有一定影响，水力旋流器的直径变化和锥段角度变化对分流比基本上没有影响；随着直径、锥段角度的增大，分离粒度逐渐增大，回收率降低；随着入口压力增大，水力旋流器的分离粒度变小，底流的分流比会缓慢增加；随着溢流管管径的增加，分离粒度增大，分流比明显减小，回收率降低；随着底流管直径的增加，分离粒度减小，分级效果明显下降，回收率会增加。

The co-channel interference canceler includes: an NTSC interference rejection filter for removing co-channel interference from an input signal; a noise reducer for reducing noise by removing interference other than co-channel interference from the input signal; and a selection controller for determining whether or not co-channel interference exists in the signal output from the noise-reducer and selecting the NRF when such co-channel interference exists in the noise reduced signal.

该共用频道干扰抵消器包括：一个NTSC干扰抵消滤波器用于从输入信号中消除共用频道干扰；一噪声消减器用于从输入信号中消减共用频道干扰外的其它干扰；和一选择控制器用于产生一选择信号，用以通过确定来自噪声消减器的信号输出中是否存在共用频道干扰来选择NRF。

Objective:To explore the feasibility of laparoscopy in diagnosing and treating of abdominal diseases.

目的：探讨腹腔镜用以诊断腹部外科疾病及选择治疗方案的可行性。

The lifetime of nylon 1010 and nylon 1010/POSS composites decreased with increasing temperature.

热重-红外联用分析表明尼龙1010在氮气气氛下的降解产物主要为小分子的低聚物，POSS并不改变尼龙1010降解产物的组成。