共查询到19条相似文献,搜索用时 203 毫秒
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针对高动态环境下扩频信号的载波捕获与跟踪问题,本文分析了多普勒频移对锁相环、锁频环以及环路滤波器设计的影响,以及高动态环境中载波快速捕获问题,在此基础上提出了一种数字复合软环的设计方法,计算机仿真结果表明这种数字复合软环能有效地解决载波快捕与精跟踪的问题. 相似文献
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高动态下GPS信号的捕获和跟踪技术研究 总被引:2,自引:0,他引:2
为检测高动态GPS信号,需要设计码环及载波环的捕获和跟踪数字系统。如何快速捕获信号,并进行精确跟踪,是问题的关键。针对高动态环境下GPS信号的捕获和跟踪问题,分析了高动态环境对GPS信号的影响,提出了FFT码快速捕获算法,以及二阶FLL与三阶PLL混合载波跟踪方案,并对码环和载波环的结构和参数的设计方法进行了说明。仿真结果和分析表明该方案能在高动态环境下实现信号的快速捕获,且能较好地满足接收机动态性能和跟踪精度的要求。 相似文献
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为了满足高动态环境下对测轨定位的需求,对数字中频接收机载波同步跟踪关键技术进行了研究。针对高动态环境下载波同步需要解决的捕获带宽、捕获速度与跟踪精度的矛盾,综合利用了传统数字锁频环路和数字锁相环路的优点,设计了一种适合高动态环境下数字中频接收机的锁频联合锁相环工作的环路方案。仿真和测试结果表明:改进算法解决了环路跟踪精度和动态性能不能兼顾的矛盾,信号跟踪环路能在高动态环境中实现对信号的稳定跟踪。 相似文献
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基于卫星通信高动态、高精度的需求,提出了一种锁频环与锁相环相结合的双环载波跟踪系统.通过分析热噪声和动态应力对载波环跟踪精度的影响,指出了锁相环和锁频环的优缺点,给出了复合载波环的结构框图和工作流程.最后通过系统仿真,证明了复合载波环比单一载波环具有更全面的性能. 相似文献
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提出一种具有串联环路结构的新型数字载波跟踪环,以解决极低载噪比下高动态载波信号的跟踪问题.在输入加性高斯白噪声假设下,通过建立具有一定通用性的Z域全相位模型,对新型载波环的噪声跟踪性能进行了理论分析,推导出相位噪声方差的计算通式.根据新型载波环的具体实例,验证了理论分析结果的正确性.基于上述分析结果,对新型载波环完成了参数优化,并对其与传统载波环进行了性能比较.结果表明,在极低载噪比高动态条件下,新型载波环跟踪性能优于传统载波环.所得结论可用于评估新型载波环的噪声跟踪性能或指导其环路设计. 相似文献
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针对扩频体制下低轨卫星信号的捕获及跟踪等系统设计实现问题,根据卫星信号模型进行了捕获及跟踪算法设计,重点对基于快速傅里叶变换的快速捕获算法、锁频环、锁相环和码跟踪环路进行了设计,并进行了工程系统实现。试验验证表明,该系统可以实现码分多址体制低轨卫星信号捕获、跟踪处理,工作性能参数满足系统需求。 相似文献
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This paper investigates several key questions concerning the mechanization and design of a Costas receiver for reconstruction of a carrier from a suppressed carrier signal. For baseband NRZ encoded data symbols and a soft bandpass limiter preceding the loop, several design issues which are considered herein and which affect acquisition and tracking performance are: (1) The choice of an IF bandwidth. (2) The optimum choice of the Costas arm filter bandwidths as well as the spectral roll-off characteristics. (3) The optimum choice of loop bandwidth to data rate ratio for a given signal-to-noise ratio. (4) The signal suppression factor and the combined limiter-squaring loss. (5) The variations in loop bandwidth and damping with signal level. (6) The choice of the limiter transfer characteristic. (7) Performance degradation due to the presence of a limiter. Various new results in system design are presented and typical numerical results are given and graphically demonstrated in SNR regions of practical interest. The theory is applicable to the design of carrier reconstruction loops required in the implementation of spread spectrum communication receivers. 相似文献
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Wei‐Lung Mao An‐Bang Chen 《International Journal of Satellite Communications and Networking》2008,26(2):119-139
Carrier phase information is necessary for accurate measurements in global positioning system (GPS) applications. This paper presents a novel intelligent GPS carrier tracking loop with variable‐bandwidth characteristics for fast acquisition and better tracking capability in the presence of dynamic environments. Our dual‐loop receiver is composed of a frequency‐locked loop‐assisted phase‐locked loop structure, the fuzzy controllers (FCs), and the ATAN discriminator functions. The soft‐computing FCs provide the time‐varying loop gains to perform accurate and reliable control of the dual‐loop paradigm. Once the phase dynamic errors become large under kinematic conditions, the fuzzy loop gains increase adaptively and achieve rapid acquisition. On the other hand, when the tracking errors approach zero in the steady state, the loop gains decrease and the corresponding dual‐loop receiver returns to a narrowband system. Four types of carrier phase signals, i.e. phase offset, decaying sinusoidal phase jitter, frequency offset, and frequency ramp offset, are considered to emulate realistic mobile circumstances. Simulation results show that our proposed receiver does achieve a superior performance over conventional tracking loops in terms of faster settling time and wider acquisition range while preventing the occurrence of cycle slips. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
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This paper presents the root-mean-squared tracking error performance analysis of a class of coherent digital delay-locked
loops for multicode direct sequence spread spectrum signals in bandlimited correlated Rayleigh fading channels. In the transmit
side, multiple independent PSK-modulated data streams in the in-phase and qudrature phase branches are spread by short mutually
orthogonal codes before being further complex spread by a long complex PN code. We assume that the system employs a pilot
code channel to assist the receiver’s synchronization and channel estimation. The proposed code tracking loop incorporates
the pilot-aided channel estimator and derives the timing error from all short-code-spread subchannels. Our analysis takes
into account the effects of imperfect channel estimate, correlated frequency selective Rayleigh fading and band-limiting.
Numerical results are presented to quantify the impact of the resulting multipath interference within the same code channel
and amongst different code channels. 相似文献