共查询到18条相似文献,搜索用时 218 毫秒
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载波同步模块是数字接收机最为关键的组成部分之一,本文对实现载波同步的方法进行改进,在分析了FFT频偏估计的基础上,将FFT频偏估计与极性Costas环结合,使FFT频偏估计辅助极性Costas环捕获以提升环路性能.对FFT频偏估计进行了MATLAB仿真和FPGA实现,并对改进后的极性Costas环路进行了FPGA实现. 相似文献
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基于扩频通信系统的接收机跟踪技术研究 总被引:1,自引:0,他引:1
文章在对信号的捕获方法进行了研究的基础上,将展开对扩频信号跟踪方法的研究与设计.通过对锁相环的基本原理进行阐述,采用两种特殊的锁相环--DLL和Costas环分别实现伪码跟踪环路和载波跟踪环路的设计. 相似文献
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为研究GPS信号处理技术,首先设计了GPS软件接收机的总体方案,然后对其中的关键模块——载波跟踪环进行深入分析并拟定环路各部件的实现方案,利用MATLAB对环路进行仿真分析,验证了该方案的可行性,最后在Altera公司的FPGA上完成了环路的设计.结果表明,Costas载波跟踪环性能良好,完全能够满足GPS软件接收机的工作要求,具有一定的工程参考价值. 相似文献
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对基于现场可编程门阵列(FPGA )的全数字Costas环的设计方法进行了研究。首先,基于锁相环的模型,研究了数字Costas环的结构和性能,详尽的分析了数字Costas环的原理。然后,对数字Costas环的所有参数公式进行了准确细致的推导,对某些重要参数公式进行了修正,以提高所设计的数字Costas环的性能。最后,采用Ver-ilog HDL硬件描述语言,在Xilinx FPGA上开发了数字Costas环的各个模块,并综合成一个完整的Costas环。结合一个实际案例给出了实现后的数字Costas环的寄存器传输逻辑(RTL)原理图和仿真结果。仿真数据证明按照该设计方法和修正后的参数公式可以设计出实用的、性能十分优良的全数字Costas环。 相似文献
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相比于传统的单一的雷达或通信设备,雷达通信一体化系统具有易集成、小型化、高谱效等优势,其中基于线性调频的一体化信号的系统方案应用广泛。在一体化系统通信功能实现方案中,传统的同步技术会降低通信速率。针对这一问题,设计了一种包含两类线性调频载波的一体化信号,并利用线性调频良好的自相关特性,提出了一种基于Costas环的时间和载波频率联合同步技术。在该技术中,首先设计了基于线性调频的Costas环结构,实现对两类调频载波的跟踪,然后根据两类载波的频率信息反演出通信时延和载波频偏。仿真结果表明,该同步技术在不影响通信效率及雷达性能的情况下,可实现一体化信号的时频联合同步,且误码率与传统同步技术的性能相当。 相似文献
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BPSK、QPSK、OQPSK、8PSK 和 16QAM 在数字通信中应用广泛。针对非合作接收机解调数字通信信号的需求,研究了基于 Costas 环的通用数字信号载波恢复技术。仅需通过调整环路滤波参数和改变 Costas 环中鉴相器的鉴相方式,即可实现 BPSK、QPSK、OQPSK、8PSK 和 16QAM 等数字信号的载波恢复。对算法进行了仿真验证,并在 FPGA 上完成了硬件实现。 相似文献
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Improving Frequency Acquisition of a Costas Loop 总被引:1,自引:0,他引:1
A Costas loop for tracking a BPSK signal does not acquire when the initial frequency error is comparable to the loop bandwidth. This paper describes methods for deriving control proportional to frequency error so as to improve the frequency acquisition capability by an AFC augmentation. A composite AFC/Costas loop is realized by combining the individual loops. Pull-in from a frequency error much greater than the Costas loop bandwidth is now feasible. The increase in phase error due to the AFC capability is evaluated by a linearized analysis. If the bandwidth of the AFC portion is sufficiently narrow, the degradation is negligible. Improved frequency acquisition can also be realized by a simple modification of the Costas loop to remove the low-pass filter on the quadrature phase detector channel, with negligible degradation to phase tracking. 相似文献
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基于锁相环的模型,研究了数字Costas环的结构和性能.首先介绍了Costas环的基本原理及数学模型,其次使用matlab编程的方法实现了软件上的仿真,最后在QuartusⅡ+ModelSim环境中用VHDL语言实现了该算法.仿真和实验结果表明,该Costas环路具有十分优良的性能. 相似文献
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It is becoming increasingly popular in the design of suppressed carrier receivers, which employ Costas loops for earrier reconstruction, to hard-limit the output of the in-phase channel. Doing so allows replacement of the analog multiplier, which forms the loop error signal, with a chopper-type device which typically exhibits much less dc offset. The false lock behavior of such a hard-limited loop was recently investigated and shown to be quite different from that of the conventional Costas loop without the hard limiter. This paper presents the companion, analysis of the tracking performance of the hard-limited loop and assesses the penalty, if indeed it is a penalty rather than an improvement, in this performance relative to the conventional Costas loop with an analog third multiplier. In particular, for the case ofRC arm filters and NRZ data, the squaring loss (or equivalently the linear loop tracking jitter) is evaluated and illustrated as a function of the ratio of arm filter bandwidth to data rate and data signal-to-noise ratio. Superimposed on these numerical results will be the corresponding ones for the conventional Costas loop. As a finale, the equivalence in operation of the Costas loop with hard-limited in-phase channel and a baseband modulation carrier reconstruction loop referred to as a demod/ remod loop is discussed. 相似文献
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The frequency and phase acquisition performance of three quadrature phase shift keying (QPSK) carrier tracking loops, the MAP estimation loop, the Costas crossover loop, and the generalized Costas loop, is described. Acquisition time and probability of acquisition as a function of both loop signal-to-noise ratio and frequency offset to loop bandwidth ratio are obtained via computer simulations for type II and III loops. It is shown that the MAP loop, which results in the smallest squaring loss for all signal-to-noise ratios, is sometimes outperformed by the other two loops in terms of acquisition time and acquisition probability 相似文献
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Costas loops are invariably designed in conjunction with an automatic gain control (AGC) loop for stabilizing performance. In such systems an inherent coupling between the AGC and Costas loops develops, complicating the standard phase referencing analysis. This coupling is further emphasized if the gain control amplifier introduces an AM/PM conversion, which causes power variations to enter the Costas loop as phase variations. In this paper the coupling effect between AGC and Costas loops is developed, leading to a pair of joint, interconnected dynamical tracking loops. Some degree of solution is attainable by assuming a first order AGC loop, and resorting to quasi-stationary analysis for evaluating the phase referencing generation. Results with and without AM/PM are presented, and illustrate how an improper AGC may in fact degrade the phase referencing from the expected performance. 相似文献