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低轨星座接收机面临大多普勒频移及频繁快速换星等设计约束,对其载波跟踪环路设计提出了较高的动态适应性与跟踪精度要求。针对以上问题,提出了一种基于参数控制的载波跟踪算法。该算法引入环路控制因子参数,将环路滤波器分为牵引和跟踪两阶段。基于理论建模推导环路控制因子的最优参数配置原则,指导实现牵引和跟踪两种状态滤波器的协同配合,在牵引阶段有效引导大多普勒信号快速入锁,在跟踪阶段精确估计载波频移参数,实现基于低轨星载平台的GNSS信号快速准确跟踪。理论与仿真结果均表明基于参数控制的载波跟踪算法能够有效提升环路的动态适应性与跟踪精度,满足低轨星载接收机的设计需求。与传统算法相比,该算法在保证信号跟踪精度的同时,能够将收敛时间缩短78%,且环路设计简单,易于硬件实现。 相似文献
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This paper derives and graphically illustrates the performance characteristics of Phase-Shift-Keyed communication systems where the receiver's phase reference is noisy and derived from the observed waveform by means of a narrow-band tracking filter (a phase-locked loop). In particular, two phase measurement methods are considered. One method requires the transmission of an auxiliary carrier (in practice, this signal is usually referred to as the sync subcarrier). This carrier is tracked at the receiver by means of a phase-locked loop, and the output of this loop is used as a reference signal for performing a coherent detection. The second method is self-synchronizing in that the reference signal is derived from the modulated data signal by means of a squaring-loop. The statistics (and their properties) of the differenced-correlator outputs are derived and graphically illustrated as a function of the signal-to-noise ratio existing in the tracking filter's loop bandwidth and the signal-to-noise ratio in the data channel. Conclusions of these results as well as design trends are presented. 相似文献
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为解决环路未锁定、无法找出正确的导航数据位跳变点时极弱全球定位系统(GPS)信号跟踪问题,通过分析信号跟踪模型和相关器1 ms采样数据特性,将最优路径动态规划算法应用于GPS位同步,并提出基于平方根无迹卡尔曼滤波(SRUKF)和位同步结合的载波联合跟踪算法。建立了适合位同步的SRUKF载波环参数估计模型,针对位同步的实现条件和无相位频率先验信息的情况,将位同步模块提前,研究设计了环路未锁定时串行和并行两种弱信号跟踪方案。位同步跟踪完成后环路采用单独的SRUKF工作方式。实验结果证实该文提出的算法具有较高的数据位边缘检测概率(EDR)和参数估计性能,而无须关心环路是否处于锁定状态,能够对载噪比低至22 dB/Hz的弱信号实现跟踪。 相似文献
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Performance analysis of GPS carrier phase observable 总被引:3,自引:0,他引:3
The accuracy analysis of Global Positioning System (GPS) carrier phase observable measured by a digital GPS receiver is presented. A digital phase-locked loop (DPLL) is modeled to extract the carrier phase of the received signal after a pseudorandom noise (PRN) code synchronization system despreads the received PRN coded signal. Based on phase noise characteristics of the input signal, the following performance of the first, second, and third-order DPLLs is analyzed mathematically: (1) loop stability and transient process; (2) steady-state probability density function (pdf), mean and variance of phase tracking error; (3) carrier phase acquisition performance; and (4) mean time to the first cycle-slipping. The theoretical analysis is verified by Monte Carlo computer simulations. The analysis of the dependency of the phase input noise and receiver design parameters provides with an important reference in designing the carrier phase synchronization system for high accuracy GPS positioning 相似文献
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基于UKF准开环结构的高动态载波跟踪环路 总被引:2,自引:1,他引:1
对高动态环境下的全球卫星导航系统(GNSS)载波信号跟踪方法进行了研究。在分析高动态载波信号模型的基础上,提出了一种基于无迹卡尔曼滤波(UKF)的准开环载波跟踪方法。此方法能够消除导航数据二进制相移键控(BPSK)调制的影响,并采用四维UKF相位估计模型提高跟踪精度,同时对估计值进行补偿以减少滤波器的滞后性。通过模拟接收机的高动态运动轨迹,从跟踪误差、跟踪结果和补偿效果3个方面,与基于卡尔曼滤波(KF)的锁频环(FLL)辅助锁相环(PLL)结构的传统跟踪方法进行比较,结果表明基于UKF的准开环跟踪方法能够有效地完成高动态环境下的载波跟踪。 相似文献
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Aiming at mitigating multipath effect in dynamic global positioning system (GPS) satellite navigation applications, an approach based on channel blind equalization and real-time recursive least square (RLS) algorithm is proposed, which is an application of the wireless communication channel equalization theory to GPS receiver tracking loops. The blind equalization mechanism builds upon the detection of the correlation distortion due to multipath channels; therefore an increase in the number of correlator channels is required compared with conventional GPS receivers. An adaptive estimator based on the real-time RLS algorithm is designed for dynamic estimation of multipath channel response. Then, the code and carrier phase receiver tracking errors are compensated by removing the estimated multipath components from the correlators’ outputs. To demonstrate the capabilities of the proposed approach, this technique is integrated into a GPS software receiver connected to a navigation satellite signal simulator, thus simulations under controlled dynamic multipath scenarios can be carried out. Simulation results show that in a dynamic and fairly severe multipath environment, the proposed approach achieves simultaneously instantaneous accurate multipath channel estimation and significant multipath tracking errors reduction in both code delay and carrier phase. 相似文献
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Carrier loop architectures for tracking weak GPS signals 总被引:8,自引:0,他引:8
Razavi A. Gebre-Egziabher D. Akos D.M. 《IEEE transactions on aerospace and electronic systems》2008,44(2):697-710
The performance of various carrier recovery loop architectures (phase lock loop (PLL), Doppler-aided PLL, frequency lock loop (FLL), and Doppler-aided FLL) in tracking weak GPS signals are analyzed and experimentally validated. The effects of phase or frequency detector design, oscillator quality, coherent averaging time, and external Doppler aiding information on delaying loss of lock are quantified. It is shown that for PLLs the metric of total phase jitter is a reliable metric for assessing low C/N performance of the tracking loop provided the loop bandwidth is not too small (~> 5 Hz). For loop bandwidths that are not too small, total phase jitter accurately predicts carrier-to-noise ratio (C/N) at which loss of lock occurs. This predicted C/N is very close to the C/N predicted by bit error rate (BER). However, unlike BER, total phase jitter can be computed in real-time and an estimator for it is developed and experimentally validated. Total phase jitter is not a replacement for BER, since at low bandwidths it is less accurate than BER in that the receiver loses lock at a higher C/N than predicted by the estimator. Similarly, for FLLs operating at small loop bandwidths, it is found that normalized total frequency jitter is not a reliable metric for assessing loss of lock in weak signal or low C/N conditions. At small loop bandwidths, while total frequency jitter may indicate that a loop is still tracking, the Doppler estimates provided by the FLL will be biased. 相似文献
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Coherent demodulation of a PSK signal requires the generation of a local carrier phase reference. Methods are given to determine the detection loss caused by noisy phase recovery and its use in the coherent detection of filtered BPSK and QPSK signals. It is assumed that the phase noise can have a static part and a random component with a Tikhonov-type distribution. The static part is mostly due to offset frequency tracking of the PLL used to recover the carrier, while the random component is due to thermal noise present in the carrier recovery loop and is also due to the random nature of the phase modulation. It is shown that the probability of error of BPSK and QPSK can be expressed as a finite sum of a set of strictly alternating converging series when the number of ISI terms is finite. Upper and lower bounds on the probability of error have been derived when this number becomes infinite and we show how this error rate can be computed with any desired accuracy. Numerical results are presented for various values of static error and phase noise variance when the transmit and receive filters are 4-pole Butterworth filters. For filtered PSK signals and for a bit error rate of 10-6, our results show that the additional degradation in presentday receiver systems due to imperfect carrier recovery can be less than 0.1 dB for BPSK and less than 1 dB for QPSK. 相似文献
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为了提高北斗导航接收机的灵敏度,提升其弱信号跟踪能力,通常需要利用长时间的相干积分来提高环路信噪比。但是,当相干积分时间加长到一定程度时,环路性能反而有所下降,信噪比提升也不能达到理论值。针对由剩余频率误差和晶振误差引起的相干积分能量损失问题,主要研究了频率偏差对环路跟踪性能的影响,并提出了利用频率稳定度传递策略辅助弱信号跟踪的方法,解决了北斗导航接收机弱信号跟踪性能提升的问题,最大程度地改善了相干积分的效果,实现了对弱信号的跟踪。利用软件接收机平台对提出的频率稳定度传递算法进行验证,仿真结果表明该算法可使环路信噪比提升4dB ~5dB,充分说明了其可行性及有效性。 相似文献
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针对目前编码辅助载波同步算法中复杂度较高、延时大的问题,提出了引入辅助停止判决机制的编码辅助载波同步算法。在现有的编码辅助载波同步结构基础上,该算法能对环路信噪比(SNR)进行实时判定,在环路SNR满足限定条件后提前停止编码辅助载波同步迭代,而不影响译码性能。采用新的相位估计方式估计含相位噪声的载波相位,提升了该条件下的环路信噪比。仿真采用码率为1/2的低密度奇偶校验(LDPC)码作为编码方式,结果表明:在误码率为10-5时,该算法减少了约50%的编码辅助载波同步迭代次数;在含相位噪声的信号条件下,与理想解调译码相比,性能损失不超过0.15 dB。 相似文献
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Two different implementations of the carrier recovery loop for suppressed carrier binary phase-shift keyed (BPSK) signals are considered. In particular, the tracking performance of the squaring loop in which the squaring circuit is mechanized by a limiter/multiplier lier combination to produce the absolute value of the incoming signal, followed by appropriate bandpass filtering, is compared with that of the usual squaring loop whose squaring circuit is the timestwo wo multiplier which exhibits a square law characteristic. 相似文献
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扩频通信系统伪码相位跟踪环性能研究 总被引:3,自引:0,他引:3
在现代通信系统中,对于全数字化扩频接收机来说,由于伪码跟踪环中鉴相器具有非线性特性,所以有可能使扩频通信环路工作在非线性区域。本文分析了一种非相干伪码跟踪环路的线性以及非线性跟踪性能,并得到了环路的收敛域与收敛条件,这些分析结果对环路参数的设计都是至关重要的。 相似文献
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A new type of phase detector for pseudonoise code tracking is introduced and analyzed in comparison with the delay lock loop (DLL) and tau-dither loop (TDL) configurations. It is shown that the double dither loop (DDL) combines the best features of the DLL and the TDL in that the DDL is insensitive to gain and offset imbalances and does not suffer the 3-dB degradation in noise performance typically associated with the TDL. The double dither concept is applicable to other dual channel detectors such as in a Costas-type carrier tracking loop. 相似文献