查询词典 SNR

It was shown that the SNR of the RADS could be improved by using a microwave cavity with proper microwave field mode and high microwave filling factor, a rubidium spectrum lamp with high spectrum purity and a separated isotope filtering scheme in the physics package design. The performance of the rubidium atomic frequency standard could be improved by taking all these factors into consideration.

本文分析了微波腔的结构、铷光谱灯的光谱纯度和同位素滤光方案对信噪比的影响，指出采用模式优越、微波填充因子大的微波腔，光谱纯度高的铷光谱灯，用分离滤光方法进行同位素滤光，可以提高铷原子鉴频信号的信噪比，从而使铷频标的稳定度指标得到进一步改善。

The paper investigates both block-type pilot linear minimum mean square error algorithm and IEEE802.16 OFDM channel estimation analysis. Simulation results confirm the block-type pilot structure is more suitable for IEEE802.16 system. An optimal pilot setting algorithm, based on space frequency domain, is explored and the pilot chart is presented. The proposed algorithm finds its application in MIMO-OFDM. Simulation results show the algorithm presents a good approximation to the perfect channel state information curve, with about 2dB difference in SNR. The simulation results also demonstrate the algorithm achieves fairly high stability in the environment of fast fading, performance of the proposed algorithm is better that of pilot training channel estimation.3. Taking into account the characteristics of IEEE802.16 OFDM system, OFDM system simulation platform is constructed in Matlab, exploiting simulink as a tool. OFDM modulation and demodulation simulation system are configured on LabVIEW platform. All the system signal processing is simulated, including defining system parameters, designing modulation model, and verifying all the proposed algorithms under different environments, such as white Gaussian noise, multi-path fading, with or without guard interval etc. Bit error performance is evaluated. The research provides valid theoretical basis for practical OFDM system performance evaluation.4. Taking advantage of software radio, the paper designs a hardware platform with both 256-IFFT/FFT and 512-IFFT/FFT OFDM schemes co-existing in one platform. You can predetermine one from the two schemes to carry out almost the same model function with different system performance and parameter setting.5. Referring to IEEE802.16 standard, the paper proposes a design method for generating signals and frames suitable for laboratory investigations implemented in laboratory environment.6. Based on 6701evm digital evaluation card, combined with analogy front-end, the paper designs a DSP software model to deal with baseband signal processing. An overall OFDM scheme, with modulation and demodulation function, is accomplished.

讨论分析了MIMO-OFDM中一种基于空频域的最优导频设置算法，给出了导频图案，通过仿真实验表明，该算法与理想的信道状态信息曲线非常接近，信噪比差距约在2dB左右，并且在快衰落条件下具有较好的稳定性，其性能要优于基于前导训练的信道估计方法。3、根据IEEE802.16OFDM系统特点，论文分别在Matlab中应用Simulink工具构建OFDM系统仿真平台、在LabVIEW平台上实现了OFDM调制解调仿真系统，模拟了整个系统的信号流程，进行了OFDM仿真系统参数的选择和调制模块的仿真设计、论证各算法性能，并根据各种不同的条件：例如高斯噪声、多径衰落、有无保护间隔等，对系统的误码特性进行了评估，为正确评价实际OFDM系统的性能提供了有效的理论依据。4、论文以软件无线电思想作为指导，提出了以256点IFFT／FFT为核心和以512点IFFT／FFT为核心的两种OFDM算法模式并存于同一个硬件平台、且可预选的方案，它们在参数选取和性能指标上有所差异，均实现了相似的模块和功能。5、论文参考IEEE 802.16无线网络标准的参数设置，针对本设计系统的应用环境和系统硬件的性能速率，提出了一种应用于实验室环境的信号结构、帧格式等参数设计。6、论文基于TI公司的6701evm数字评估板卡，结合模拟前端搭建数字中频平台，设计了基带处理的DSP软件模块并进行系统调试，基本实现了一套完整的OFDM调制解调方案。

Simulations indicated that, in the condition of without any preambles, carrier phase could be acquired fast and tracked steadily, and this scheme still worked well even in low SNR level condition.

软件仿真结果表明，该方法能快速恢复和跟踪载波相位，即使在较低的信噪比情况下，解调系统也能正常工作。

Finally both SNR and slope of modulation transfer spectra of I2 with different absorption length were compared experimentally while I2 cell temperature was held at -15 ℃. The results of comparison showed that modulation transfer spectra was optimal at three-pass (120 cm).

实验上比较了碘池温度为-15 ℃时一倍程(40 cm)，二倍程(80 cm)，三倍程(120 cm)和四倍程(160 cm)的光谱信号信噪比和谱线中心斜率，得到三倍程时信号信噪比和谱线中心斜率为最大，估算得到相应的激光稳频精度为9×10-14(1 s积分时间)。

All available three-component time series are used to extract the Rayleigh and Love waves. The Signal-to-Noise Ratio at different periods and the azimuth distribution of the inter-station pairs with high SNR are discussed.

通过对三个分量记录的相关运算，获得了Rayleigh波和Love波的经验格林函数，分析了其信噪比随周期的变化和高信噪比台站对的方位分布。

The experiment shows that this method has high detection performance for the small target in single frame at low SNR.

实验结果表明，在低信噪比情况下，算法有很好的检测性能。

The results of the study showed that:① Using dozens of kilograms of explosives the signal can be detected at distances up to 200 km;②Active source has a certain degree of repeatability among different shots;③This paper presents the following shooting mode and signal detection method based on the similarity of different shots: In light of the similarity between the signals of big shot and small shot, this paper presents a cross-correlation method using signal from big shot signal with high SNR and small shot signal to detect weak small shot signal, the method can effectively detect the small shot signal and pick up the start time of phase, this method can help us make full use of past seismic exploration data records.

野外实验采用1次大当量激发和16次小当量激发，研究结果表明：①有可能利用数十公斤当量的炸药实现200km距离的探测；②在激发条件相同时，不同当量的激发波形滤波后存在一定的相似性；③依据人工震源可重复性采用以下的激发组合方式和处理方法能够有效提高信噪比：针对大当量激发与小当量激发波形的相似性，利用大当量激发的波形作模板与小当量激发的波形作相关，可判断台站是否接受到小当量激发的信号并检测其震相到时信息。

The PBR and PD of propeller shaft frequency with different sound pressures and acoustic vector signals were calculated under various noise backgrounds and different SNR.

不同输入信噪比的常规声压与声矢量信号非整数维谱的轴频PBR及PD进行了详细计算。

First, the atmospheric influence on FSO system and the character of atmospheric channel are analyzed, the SNR of atmospheric channel versus the weather visibility is deduced, and the coding and decoding principles of twofold turbo code are analyzed.

从研究大气对自由空间光通信系统的影响出发，在分析了大气信道特性后建立了大气信道信噪比和能见度的关系，详细阐述了双模turbo码的编码、译码原理。

The central problem in our work is to lower down the signal-to-noise ratio threshold of super-resolution.

本文的研究是围绕如何降低超分辨处理适用的SNR门限这一关键问题展开的。

However, as the name（read－only memory）implies, CD disks cannot be written onorchanged in any way.

然而，正如其名字所指出的那样，CD盘不能写，也不能用任何方式改变其内容。

Galvanizes steel pallet is mainly export which suits standard packing of European Union, the North America. galvanizes steel pallet is suitable to heavy rack. Pallet surface can design plate type, corrugated and the gap form, satisfies the different requirements.

镀锌钢托盘多用于出口，替代木托盘，免薰蒸，符合欧盟、北美各国对出口货物包装材料的法令要求；喷涂钢托盘适用于重载上货架之用，托盘表面根据需要制作成平板状、波纹状及间隔形式，满足不同的使用要求。