查询词典 frequency channel

to reduce the impact of carrier frequency offset in ofdm system,this thesis designs a new carrier frequency offset estimation scheme for ofdm system.the carrier frequency offset estimation includes acquisition and tracking.we adopt variable step size adaptive algorithm.the acquisition range of the proposed algorithm is as large as one half of the overall signal bandwidth.through this method we can not only avoid the feedback by using forward error correction,but also reduce the times of complex multiplication in order to reduce the power consumption of the system.this algorithm not only has low complexity and fast convergence nut also can improve the demodulation performance of ofdm system.computer simulation illustrates the superior performance of the proposed algorithm with regard to estimation accuracy in both awgn channel and multi—path channel.

摘 要：为了减小正交频分复用系统受频率偏差的影响，在ofdm系统中设计了一种新的载波频偏估计算法。频偏估计包括跟踪和捕获两个阶段，文中采用变步长自适应算法来进行跟踪，这个跟踪算法的捕捉范围是整个信号带宽的一半。通过此方法，不但可以利用前向纠错的方式来避免反馈，而且可以缩减复数乘法的次数以降低计算复杂度和系统功耗。该方法运算复杂度低，并具有较好的收敛性，能改善odfm的解调性能。从计算机的仿真效果可以看出无论是在awgn信道上还是在多径信道上都表现出了卓越的性能。

a scheme of channel estimation using cyclic prefix based on the measurement of the low-voltage power line channel model is presented.after obtaining the frequency response of pilot sub-channel under the state of comb-type pilot,the data sub-channel response is obtained by interpolating the frequency response in frequency direction.in the pilot-free data period,the estimation of the channel is carried out by using cyclic prefix in order to improve the performance of system error rate.

摘 要：通过实际测量给出低压电力线的信道模型，在此基础之上提出了利用循环前缀对信道进行估计的方法，即在梳状导频模式时，使用导频获得导频子信道频率响应后，对其在频域方向进行插值得到数据子信道响应，在其后没有导频的序列的数据周期内，使用循环前缀对信道进行估计，从而起到改善系统误比特性能的目的。

Finally the main parameters of the radio frequency channel are tested and the results are given.

最后本文对射频信道的主要指标进行了测试，给出了测试结果。

The design includes hardware and software,implements basis control for volume of sound and frequency channel.

该设计包括硬件和软件两部分，实现对电视音量和频道的基本控制。

Spectral efficiency equations are derived for both systems with and without channel prediction. Numerical results show that systems with channel prediction can get maximum spectral efficiency while systems without channel prediction but chosen optimum packet length can get suboptimum frequency efficiency, which is inversely proportional to Doppler frequency.

推导了信道预测和没有信道预测的自适应调制系统的频谱效率公式，分析结果表明对于自适应调制系统，信道预测的系统频谱效率是最优的，非信道预测系统根据信道情况选择最优帧长可以获得该系统的最优系统频谱效率，但它是低于信道预测的频谱效率的，而且是随多普勒频率的增大而逐渐减小的。

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 digitalsignal carries on the long distance transmission, the high frequencycomponent weaken increases along with the distance increases, theelectric cable median line also advances to the betweenelectromagnetic radiation along with the frequency intensifies, thusthe clipped wave transmitting range and the transmission quality,simultaneously in the channel often also exists separates the directcurrent electric capacity and the coupling transformer, they cannottransmit the direct component and have a bigger weaken to the lowfrequency component, therefore high frequency and low frequency arepartial regarding the common channel is limited.

当数字信号进行长距离传输时，高频分量的衰减随距离的增大而增大，电缆中线对之间的电磁辐射也随着频率的增高而加剧，从而限制信号的传输距离和传输质量，同时信道中往往还存在隔直流电容和耦合变压器，他们不能传输直流分量及对低频分量有较大的衰减，因此对于一般信道高频和低频部分均是受限的。

The AGC technology in the radio frequency channel is also studied.

研究了射频信道中的自动增益控制技术。

The radio frequency channel is analyzed in detail.

重点分析了防撞雷达的射频信道部分。

It has been proved that Reichardt's Elementary Motion Detector can perform figure-ground discrimination efficiently, and Wavelet transform analysis is similar to the multi-frequency channel of human vision. So we combine EMD, Wavelet transform and Pyramid image processing together, to propose a new motion estimation algorithm. The computer simulation results reveal that the proposed algorithm can well simulate vistual motion evaluation.

本文利用Reichardt的相关型初级运动检测器二维阵列可以有效地进行图象－背景相对运动分辨的特点，以及小波变换的频谱分析特性与人类视觉多频率通道特性相类似的性质，将EMD模型、小波变换和图象的塔式结构处理有机地结合起来，提出了一种类似视觉信息加工方式的新的运动分析算法。

With Death guitarist Schuldiner adopting vocal duties, the band made a major impact on the scene.

随着死亡的吉他手Schuldiner接受主唱的职务，乐队在现实中树立了重要的影响。

But he could still end up breakfasting on Swiss-government issue muesli because all six are accused of nicking around 45 million pounds they should have paid to FIFA.

不过他最后仍有可能沦为瑞士政府&议事餐桌&上的一道早餐，因为这所有六个人都被指控把本应支付给国际足联的大约4500万英镑骗了个精光。