共查询到19条相似文献,搜索用时 116 毫秒
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直接序列扩频技术在现代无线通信系统中有着广泛的应用,该信号的数字接收是实现对其侦察截获的关键技术之一。本文介绍了直接序列扩频技术原理及其在cdma2000移动通信系统中的应用,提出一种针对cdma2000直接序列扩频信号的零中频数字接收算法,并详细给出了码捕获及跟踪算法、载波同步算法的数学模型推导。实验结果显示,该算法成功地实现了码同步及载波同步,有较好的解调效果。 相似文献
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扩频信号的捕获与跟踪是扩频接收机进行定位解扩的基础,文中基于FPGA进行了扩频信号捕获与跟踪的设计实现。分析了该方案的匹配滤波器、载波跟踪环、码跟踪环的设计与实现方法。并通过BPSK调制,使用非相干扩频通信的PN码并行捕获算法实现信号的捕获。 相似文献
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针对新一代M码卫星导航信号解调分析问题,在比较两种捕获方法特点的基础上,本文从工程可实现的角度提出了一种M码导航信号直接捕获方法,采用扩频码同步、载波剥离和亚载波剥离等技术,直接对载波C/A码、P(Y)码和M码复用信号进行解调处理.仿真结果表明,本文方法可以有效地降低C/A码和P码信号对于M码信号接收的影响,能够准确地恢复出原始扩频序列. 相似文献
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针对同阶二元偏移载波调制卫星导航信号,提出一种高效新算法解决信号跟踪中的模糊性。分析了同阶二元偏移载波调制原理、信号跟踪模糊性及解决方法,利用本地扩频码与接收信号的相关函数特点,构建了码跟踪环路鉴相曲线,选择了合适的相关间距作为符号判决,联合构成鉴相器,推导了算法设计的正确性,给出了实现架构。仿真结果表明,码相位捕获误差±0.9个码片内均可正确跟踪。该方法可进一步应用于全球卫星导航系统新体制信号的接收处理。 相似文献
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扩频通信接收机关键技术的FPGA实现 总被引:2,自引:0,他引:2
扩频伪码的捕获与跟踪是扩频通信接收机的关键技术,其实现十分复杂并且需要大量的软/硬件资源。为了实现接收机的小型化、降低功耗、提高系统的性能和可靠性,提出了采用FPCA实现扩频伪码的捕获与跟踪及其他关键技术,在FPCA上集成数字下变频、载波振荡器、匹配滤波器、伪码发生器、载波跟踪环、伪码跟踪环和解扩共7个模块。详细讨论了各模块的设计方案,并对扩频伪码的捕获进行了仿真,仿真结果证明了设计方案是正确的。 相似文献
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中频数字化扩频测距系统的实现 总被引:1,自引:1,他引:0
给出了统一扩频、统一信道模式的中频数字化扩频测距系统的实现方案。该系统的载波与伪随机码的捕获采用了FFT辅助捕获技术,载波的跟踪采用了数字CPAFC环路牵引、数字COSTAS环路精确跟踪技术,可以有效克服多普勒频移对系统性能的影响。GOLD码跟踪采用的是数字DLL环路,利用该扩频码与截断m序列之间具有的同速率、倍周期的关系,在GOLD码同步后引导截断m序列快速同步。讨论了实现1ns恒分辨率、误差为0.01chip的测距方法与测量数据的"置中值"链接方法。 相似文献
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The acquisition and tracking systems of a spread-spectrum receiver are probably the most critical components of the receiver, since if they fail to function properly, it is doubtful that the desired signal can be successfully detected. This means that the affect of interference (such as jamming) on the receiver while it is attempting to learn the correct phase position of the incoming code might be especially harmful, since the interference might not allow the receiver to acquire the signal. To address this problem, a narrow-band interference suppression filter is used to enhance the performance of a serial search acquisition scheme for a direct-sequence spread-spectrum receiver. Analytical expressions for the probabilities of error in both the search and lock modes are derived, and numerical results are used to illustrate the sensitivity of the receiver to various system parameters. It is shown that the presence of the rejection filter can be significantly improves the performance of the acquisition system 相似文献
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An acquisition method of long pseudo-noise (PN) sequences in direct-sequence spread spectrum (DS/SS) systems is presented. The concurrent cross correlation of locally generated auxiliary signals with the incoming PN sequence produces binary search estimates leading to an initial approximation of the input signal's PN offset. The PN receiver then uses a closed-loop subsystem to determine the true offset of the incoming PN signal. New phase estimates are generated from successive corrections of likely errors in the binary search. The acquisition scheme's average acquisition time and its variance are analytically determined. Simulation results show that the proposed acquisition scheme is faster than the conventional serial receiver. A hybrid serial/parallel PN acquisition receiver is used for comparing the acquisition performance given similar hardware complexity. The hybrid receiver used the same number of parallel correlators as used in the proposed receiver's input phase estimator. Simulation results show that the proposed system provides an improved performance under normal operating conditions. 相似文献
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This paper investigates tracking of direct-sequence spread-spectrum (DS/SS) signals based on an adaptive filtering technique. It is shown that a previously proposed hardware for code acquisition is also capable of code-tracking, and, hence, by performing both acquisition and tracking with the same circuitry, a significant simplification in the overall DS/SS receiver structure is gained. Analytical results show that the proposed scheme has a good tracking performance, as measured by the hold-in time and the false alarm penalty time, and is less sensitive to variations in the signal-to-noise ratio (SNR) compared to conventional delay-locked loops (DLLs). Moreover, simulation results show that the proposed adaptive filter tracking scheme has a smaller residual tracking error than that produced by a conventional maximum-likelihood estimator (MLE) 相似文献
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Adaptive-Array Algorithm for Interference Suppression Prior to Acquisition of Direct-Sequence Signal
Strong directional interference can prevent code acquisition in a direct-sequence system, thereby rendering the system inoperable. This paper presents a computationally simple adaptive-array algorithm that cancels directional interference prior to code acquisition when the direction of arrival of the desired signal is unknown, no pilot symbols are available, and long spreading sequences must be accommodated. The preacquisition algorithm is shown to dramatically reduce the interference level relative to that of a desired direct-sequence signal before code acquisition has been achieved. As a result, the code acquisition process is greatly facilitated. 相似文献
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We propose a closed-loop system with a pre-loop code phase estimator (PLE) for acquisition of the pseudonoise (PN) signal in direct-sequence spread-spectrum systems. It consists of two major parts: a PLE and a closed-loop acquisition subsystem. The system uses an auxiliary signal, as opposed to the PN signal itself, to correlate with the incoming signal. The PLE uses the correlation result to obtain an estimate of the incoming code phase. Then, starting with this initial estimate, the closed-loop subsystem will acquire the code phase of the incoming PN signal. With coherent carrier demodulation, mean and variance of the acquisition time of the proposed scheme are obtained and compared to those of the conventional serial-search acquisition receiver and the closed-loop system without the pre-loop estimator. Results show that, with proper choices of parameters, the proposed system acquires the PN phase significantly faster than the other two systems 相似文献
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This paper gives a general introduction to bidirectional optical intersatellite links. The design, principles and link budget are presented, and the four subsystems—transmitter, receiver, optical channel and acquisition/tracking system—are described. GaAlAs semiconductor laser and a silicon avalanche photodiode are used as the optical transmitter and receiver. Pulse polarization position modulation is used to obtain a higher sensitivity. The acquisition/tracking signal is extracted from the top-modulation data stream. The effect of background noise is analysed, and direct detection and heterodyne detection are compared. 相似文献