共查询到20条相似文献,搜索用时 218 毫秒
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采用nRF24Z1无线射频芯片对电视机顶盒的数字音频S/PDIF信号进行无线发送与接收。该方案根据实际应用环境设计电路,并采用PIC18系列单片机分别对发送端和接收端射频芯片及接收端的D/A转换芯片进行配置,并设计按键控制其音量的增减。实验表明,该方案能够实时接收机顶盒音频,且在室内收听时音质较好。 相似文献
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信道估计的主要且的是从接收端接收到的混合信号中估计出信道的特征信息。本文研究了一种基于独立分量分析进行信道特征信息估计的方法。通过本方法可以获得信道特征信息,对发送端信息进行正确的接收。该方法能较好的估计出信道参数,恢复出发送端的原始信号信息。 相似文献
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数字电影卫星分发系统是一套单点发送、多点接收的数据广播传输系统,根据数字电影发行版的分发需求特点,可支持单播、组播、广播等多元化接收控制,并允许各接收点请求不同的数据内容.发送端采用并发数据发送机制,满足影片数据文件高速、安全、稳定的通过卫星信道传输到接收端.发送端、卫星信道、接收端作为数字电影卫星分发系统的主要组成,有各自的技术特点.考虑到系统的整体结构和数字电影业务需求.在卫星信道一定的情况下,发送端的性能参数将影响整个系统的效率和稳定性.因此,系统优化重点集中在发送端的优化.通过对发送端各子系统的分析,其性能瓶颈集中在影片数据存储系统.本文从提高数据存储系统,I/O吞吐性能方面,研究系统优化的具体方法.提出采用SCSI接口RAID 0磁盘阵列的存储结构优化方案.并深入研究RAID 0模式下数据分块大小的选择对性能的影响.结合理论推导和实验分析找出符合教字电影卫星分发需求的数据分块计算公式.该优化方案已经在数字电影流动放映卫星分发系统中得到了实际应用. 相似文献
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正交频分复用多址接入无源光网络OFDMA-PON具有良好的抗色散、抗偏振模色散、带宽分配灵活等优点,极有可能成为下一代光接入网的应用接入标准。采用Matlab7.0和Optisystem 7.0软件设计了一种基于RSOA的32QAM OFDMA-PON上行传输系统。该系统相邻的ONU共享一个波长,节省波长资源,在OLT中采用注入锁定的上行波长光源,实现ONU的无色化。OLT接收端同步接收后,对共用波长的两个ONU的OFDM信号分别进行OFDM解调的方法,避免了OLT中严格的同步,降低了接收端的复杂度。 相似文献
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为解决无线网络信号在传输过程中由于受到其他信号的干扰,导致接收端接收的信号与原始信号相比存在误差的问题,该文在利用数据关联和卡尔曼滤波对信号进行融合(fusion method of signal filtering based on wavelet transform and Calman,FSWC)的基础上,利用FARIMA(p,d,q)模型和数据关联来建立一种新的信号融合算法(signal fusion based on wavelet transform and date association,SFTD)。通过仿真实验分别研究融合信号与干扰距离、发送速率、容量、功率的变化情况。仿真结果表明:随着干扰距离的增加,容量开始呈现正相关趋势,直至趋于平稳,并且发送速率、容量、功率对融合信号也产生较大影响;SFTD算法比FSWC算法具有更好的信号状态融合准确性。 相似文献
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Free space optical communications through clouds: analysis of signal characteristics 总被引:1,自引:0,他引:1
Free space optical communications (FSOC) is a method by which one transmits a modulated beam of light through the atmosphere for broadband applications. Fundamental limitations of FSOC arise from the environment through which light propagates. This work addresses transmitted light beam dispersion (spatial, angular, and temporal dispersion) in FSOC operating as a ground-to-air link when clouds exist along the communications channel. Light signals (photons) transmitted through clouds will interact with the cloud particles. Photon-particle interaction causes dispersion of light signals, which has significant effects on signal attenuation and pulse spread. The correlation between spatial and angular dispersion is investigated as well, which plays an important role on the receiver design. Moreover, the paper indicates that temporal dispersion (pulse spread) and energy loss strongly depend on the aperture size of the receiver, the field-of-view (FOV), and the position of the receiver relative to the optical axis of the transmitter. 相似文献
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The performance of a time hopping combined with pulse position modulation ultra wide band system with a nonlinear receiver using an adaptive filter and a soft-limiter in the presence of narrowband interference has been considered. This system brings a significant performance improvement compared with the system that uses an adaptive filter and a linear receiver, particularly in the case of high-interference power where its absence leads to the reception loss. Also, the proposed receiver has much better interference rejection performance compared with minimal mean-square error interference rejection, in case of high-interference power (interference to signal ratios from 30 to 65 dB). 相似文献
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Lacefield JC von Ramm OT 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》2000,47(1):222-232
A novel ultrasound imaging system has been implemented using two 32-element linear phased array transducers oriented at an angle of 40 degrees to one another. The system simultaneously acquires and displays, in real time, a conventional backscatter image and an angular scatter image formed using side-scattered echoes from the same region. The design of the system is shaped by the influence of the scatter angle on the spatial resolution and receive signal processing requirements of the instrument. The subtended scatter angles are restricted to values >90 degrees to ensure that the angular scatter receiver effectively tracks the transmitted pulse and that the spatial resolution in the two images is comparable. The system is sufficiently tolerant of small variations in the average acoustic velocity of the medium to guarantee reliable pulse tracking in biomedical applications. The angular scatter signal magnitude is significantly weighted by the directivity of the receive array. The imaging system will most effectively demonstrate angular variations in scattering at scatter angles between 125 and 145 degrees , where the angular response of the receiver is near its peak. 相似文献
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Many imperfections in a practical quantum key distribution (QKD) system have been exploited by an eavesdropper (Eve) to attack the system. However, most of these attacks will introduce perturbations to the system while collecting information about the key. For example, the phase-remapping attack [Phys. Rev. A2007,75, 032314], in which Eve performs time shift on the signal pulse from the constant acting range of the phase modulation voltage to its rising edge to introduce an imperfection, results in an quantum bit error rate (QBER) of 14.6%, which is too high and will be discovered by careful users. In this paper, a frequency shift (FS) attack on ‘plug-and-play’ QKD systems with phase-coding BB84 protocol is proposed, in which Eve introduces an imperfection by the same method as she used in the phase-remapping attack. The most novel advantage of our FS attack is that Eve can get full information without introducing detectable QBER, which is more deceptive than the phase-remapping attack. 相似文献
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Channel modeling of light signals propagating through a battlefield environment: analysis of channel spatial, angular, and temporal dispersion 总被引:2,自引:0,他引:2
Free-space optical communication (FSOC) is used to transmit a modulated beam of light through the atmosphere for broadband applications. Fundamental limitations of FSOC arise from the environment through which light propagates. We address transmitted light signal dispersion (spatial, angular, and temporal dispersion) in FSOC that operates in the battlefield environment. Light signals (photons) transmitted through the battlefield environment will interact with particles of man-made smoke such as fog oil, along the propagation path. Photon-particle interaction causes dispersion of light signals, which has significant effects on signal attenuation and pulse spread. We show that physical properties of battlefield particles play important roles in determining dispersion of received light signals. The correlation between spatial and angular dispersion is investigated as well, which has significant effects on receiver design issues. Moreover, our research indicates that temporal dispersion (delay spread) and the received power strongly depend on the receiver aperture size, field of view (FOV), and the position of the receiver relative to the optical axis of the transmitter. The results describe only specific scenarios for given types of battlefield particles. Generalization of the results requires additional work. Based on properties of the correlation, a sensitive receiver with a small FOV is needed that can find the line-of-sight photons and work with them. 相似文献
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水声脉冲信号是由一个运动平台上的发射器发射的。信号的调制方式、载频、幅度、脉宽以及周期均为未知。该文介绍了一种水声脉冲信号检测的新方法。水声脉冲信号接收机输出的短时谱重心是不断起伏的。起伏在高信噪比时会变得很小,而在低信噪比(或无信号)时会变得很大。由于,起伏的绝对偏差移动平均可用来度量起伏的大小,因此,它可以被用来检测水声脉冲信号。还介绍了新检测方法的原理、算法以及仿真结果。在海洋噪声、运动载体的辐射噪声以及小的多途干扰背景中,该方法能可靠地检测水声脉冲信号,并能同时对信号的一些参数作出估计。 相似文献
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A method is presented and analyzed for determining the impulse response and frequency response of a system using an asymmetrical stimulus signal. The considered signal is a pulse with a rapid first transition, followed by a nearly constant region, and then followed by a second transition that is much slower than the first. The advantage of such a signal is that unlike a symmetric pulse, its Fourier transform has no zeros. This allows one to divide by the Fourier transform in the data analysis. It is shown that such a pulse retains the advantages of using an impulse or steplike stimulus. Error estimates similar to those previously published for impulse and steplike stimuli are given for the asymmetric stimulus 相似文献
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利用卫星导航接收机进行高精度授时同步是一种简单有效的授时同步手段。导航接收系统时延的精确测量是进行高精度授时的前提,其输出秒脉冲信号的时延更是影响远距离授时、时间同步的关键。围绕卫星导航接收系统时延的测定,通过分析卫星导航接收机的时延构成及特点,建立了卫星导航接收机的时延构成模型,制定了便于操作的卫星导航接收机时延测定的方法,搭建了一套完整的卫星导航接收机时延测定系统,并对系统进行了标定和实验验证。 相似文献
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设计了一种基于ISP技术的线阵CCD的驱动电路和高速脉冲光谱数据采集卡,建立了一套智能化脉冲激光光谱测试系统。该系统主要由分光系统、CCD传感器、光脉冲同步信号发生器、数据采集卡及计算机等部分组成。CCD将光强信号转换为电信号输出,经A/D转换器转换后的数字信号存入数据采集卡的帧存储器中,由计算机控制进行光谱数据的分析、处理。提出了用重心法对脉冲激光器的重复频率进行评估的方法,使测量精度达到了亚像素级。对系统所用脉冲激光器谱线峰值波长的复现性进行了测量,其标准差为0.0327nm。 相似文献