Vehicle positioning with the global navigation satellite system （GNSS） in urban environments faces two problems which are attenuation and dynamic. For traditional GNSS receivers hardly able to track dynamic weak sig...Vehicle positioning with the global navigation satellite system （GNSS） in urban environments faces two problems which are attenuation and dynamic. For traditional GNSS receivers hardly able to track dynamic weak signals, the coupling between all visible satellite signals is ignored in the absence of navigation state feedback, and thermal noise error and dynamic stress threshold are contradictory due to non-coherent discriminators. The vector delay/frequency locked loop （VDFLL） with navigation state feedback and the joint vector tracking loop （JVTL） with coherent discriminator which is a synchronization parameter tracking loop based on maximum likelihood estimation （MLE） are proposed to improve the tracking sensitivity of GNSS receiver in dynamic weak signal environments. A joint vector position tracking loop （JVPTL） directly tracking user position and velocity is proposed to further improve tracking sensitivity. The coherent navigation parameter discriminator of JVPTL, being able to ease the contradiction between thermal noise error and dynamic stress threshold, is based on MLE according to the navigation parameter based linear model of received baseband signals. Simulation results show that JVPTL, which combines the advantages of both VDFLL and JVTL, performs better than both VDFLL and JVTL in dynamic weak signal environments.展开更多
Weak global navigation satellite system（GNSS） signal acquisition has been a limitation for high sensitivity GPS receivers. This paper modifies the traditional acquisition algorithms and proposes a new weak GNSS sign...Weak global navigation satellite system（GNSS） signal acquisition has been a limitation for high sensitivity GPS receivers. This paper modifies the traditional acquisition algorithms and proposes a new weak GNSS signal acquisition method using re-scaling and adaptive stochastic resonance（SR）. The adoption of classical SR is limited to low-frequency and periodic signals. Given that GNSS signal frequency is high and that the periodic feature of the GNSS signal is affected by the Doppler frequency shift, classical SR methods cannot be directly used to acquire GNSS signals. Therefore, the re-scaling technique is used in our study to expand its usage to high-frequency signals and adaptive control technique is used to gradually determine the Doppler shift effect in GNSS signal buried in strong noises. The effectiveness of our proposed method was verified by the simulations on GPS L1 signals. The simulation results indicate that the new algorithm based on SR can reach-181 d BW sensitivity with a very short data length of 1 ms.展开更多
To acquire global navigation satellite system(GNSS)signals means four-dimension acquisition of bit transition,Doppler frequency,Doppler rate,and code phase in high-dynamic and weak signal environments,which needs a hi...To acquire global navigation satellite system(GNSS)signals means four-dimension acquisition of bit transition,Doppler frequency,Doppler rate,and code phase in high-dynamic and weak signal environments,which needs a high computational cost.To reduce the computations,this paper proposes a twostep compressed acquisition method(TCAM)for the post-correlation signal parameters estimation.Compared with the fast Fourier transform(FFT)based methods,TCAM uses fewer frequency search points.In this way,the proposed method reduces complex multiplications,and uses real multiplications instead of improving the accuracy of the Doppler frequency and the Doppler rate.Furthermore,the differential process between two adjacent milliseconds is used for avoiding the impact of bit transition and the Doppler frequency on the integration peak.The results demonstrate that due to the reduction of complex multiplications,the computational cost of TCAM is lower than that of the FFT based method under the same signal to noise ratio(SNR).展开更多
随着雷达技术的广泛应用,雷达也面临诸多挑战,在对微弱目标检测时,由于直达波回波和多径回波同时存在导致无法准确检测到目标,因此通常将多径回波当作干扰。然而,可以利用多径信号中存在的目标信息来优化探测性能。因此,本文提出一种新...随着雷达技术的广泛应用,雷达也面临诸多挑战,在对微弱目标检测时,由于直达波回波和多径回波同时存在导致无法准确检测到目标,因此通常将多径回波当作干扰。然而,可以利用多径信号中存在的目标信息来优化探测性能。因此,本文提出一种新的利用多径信号增强直达波信号的微弱目标增强算法(Multipath Signal Exploitation,MSE),算法通过构造两个位移函数在距离频域慢时间域对回波进行补偿,消除了不同初始距离的影响,将多径信号回波集中在直达波所在位置。然后对补偿后的回波和直达波沿快时间维求和,进一步增强了回波的能量。此外,当存在多个目标时,MSE算法可以消除多径回波的干扰,并且利用多径回波增强多目标的信号能量,以保证在多个目标的多径环境下算法仍然有效。最后进行了仿真实验,结果证明了MSE算法在多目标场景下的有效性。展开更多
在雷达探测领域,由于线性调频(linear frequency modulation,LFM)信号近主瓣区的较高旁瓣电平,强目标旁瓣对弱目标的遮盖现象使得传统雷达对这类弱目标的检测能力大幅下降。对于这一问题,提出一种混沌波形近主瓣区低旁瓣的优化方法。该...在雷达探测领域,由于线性调频(linear frequency modulation,LFM)信号近主瓣区的较高旁瓣电平,强目标旁瓣对弱目标的遮盖现象使得传统雷达对这类弱目标的检测能力大幅下降。对于这一问题,提出一种混沌波形近主瓣区低旁瓣的优化方法。该方法在保持混沌波形优秀的抗截获和抗干扰能力的基础上,结合混沌波形较低的旁瓣电平的特性,充分利用双混沌信号设计的频谱特性和失配滤波器时频自由度来调整脉冲压缩后信号的能量分布。仿真结果表明,所设计的混沌波形具有比较好的距离分辨率,并且经失配滤波器脉冲压缩后的近主瓣区的旁瓣电平达到较低水平,对检测距离相近情况下的弱目标具有一定意义。展开更多
基金supported by the National Natural Science Foundation for Young Scientists of China(61201190)
文摘Vehicle positioning with the global navigation satellite system （GNSS） in urban environments faces two problems which are attenuation and dynamic. For traditional GNSS receivers hardly able to track dynamic weak signals, the coupling between all visible satellite signals is ignored in the absence of navigation state feedback, and thermal noise error and dynamic stress threshold are contradictory due to non-coherent discriminators. The vector delay/frequency locked loop （VDFLL） with navigation state feedback and the joint vector tracking loop （JVTL） with coherent discriminator which is a synchronization parameter tracking loop based on maximum likelihood estimation （MLE） are proposed to improve the tracking sensitivity of GNSS receiver in dynamic weak signal environments. A joint vector position tracking loop （JVPTL） directly tracking user position and velocity is proposed to further improve tracking sensitivity. The coherent navigation parameter discriminator of JVPTL, being able to ease the contradiction between thermal noise error and dynamic stress threshold, is based on MLE according to the navigation parameter based linear model of received baseband signals. Simulation results show that JVPTL, which combines the advantages of both VDFLL and JVTL, performs better than both VDFLL and JVTL in dynamic weak signal environments.
基金supported by the National Natural Science Foundation of China(61202078)
文摘Weak global navigation satellite system（GNSS） signal acquisition has been a limitation for high sensitivity GPS receivers. This paper modifies the traditional acquisition algorithms and proposes a new weak GNSS signal acquisition method using re-scaling and adaptive stochastic resonance（SR）. The adoption of classical SR is limited to low-frequency and periodic signals. Given that GNSS signal frequency is high and that the periodic feature of the GNSS signal is affected by the Doppler frequency shift, classical SR methods cannot be directly used to acquire GNSS signals. Therefore, the re-scaling technique is used in our study to expand its usage to high-frequency signals and adaptive control technique is used to gradually determine the Doppler shift effect in GNSS signal buried in strong noises. The effectiveness of our proposed method was verified by the simulations on GPS L1 signals. The simulation results indicate that the new algorithm based on SR can reach-181 d BW sensitivity with a very short data length of 1 ms.
基金supported by the National Natural Science Foundation of China(61901154,41704154)Zhejiang Province Science Foundation for Youths(LQ19F010006).
文摘To acquire global navigation satellite system(GNSS)signals means four-dimension acquisition of bit transition,Doppler frequency,Doppler rate,and code phase in high-dynamic and weak signal environments,which needs a high computational cost.To reduce the computations,this paper proposes a twostep compressed acquisition method(TCAM)for the post-correlation signal parameters estimation.Compared with the fast Fourier transform(FFT)based methods,TCAM uses fewer frequency search points.In this way,the proposed method reduces complex multiplications,and uses real multiplications instead of improving the accuracy of the Doppler frequency and the Doppler rate.Furthermore,the differential process between two adjacent milliseconds is used for avoiding the impact of bit transition and the Doppler frequency on the integration peak.The results demonstrate that due to the reduction of complex multiplications,the computational cost of TCAM is lower than that of the FFT based method under the same signal to noise ratio(SNR).
文摘随着雷达技术的广泛应用,雷达也面临诸多挑战,在对微弱目标检测时,由于直达波回波和多径回波同时存在导致无法准确检测到目标,因此通常将多径回波当作干扰。然而,可以利用多径信号中存在的目标信息来优化探测性能。因此,本文提出一种新的利用多径信号增强直达波信号的微弱目标增强算法(Multipath Signal Exploitation,MSE),算法通过构造两个位移函数在距离频域慢时间域对回波进行补偿,消除了不同初始距离的影响,将多径信号回波集中在直达波所在位置。然后对补偿后的回波和直达波沿快时间维求和,进一步增强了回波的能量。此外,当存在多个目标时,MSE算法可以消除多径回波的干扰,并且利用多径回波增强多目标的信号能量,以保证在多个目标的多径环境下算法仍然有效。最后进行了仿真实验,结果证明了MSE算法在多目标场景下的有效性。
文摘在雷达探测领域,由于线性调频(linear frequency modulation,LFM)信号近主瓣区的较高旁瓣电平,强目标旁瓣对弱目标的遮盖现象使得传统雷达对这类弱目标的检测能力大幅下降。对于这一问题,提出一种混沌波形近主瓣区低旁瓣的优化方法。该方法在保持混沌波形优秀的抗截获和抗干扰能力的基础上,结合混沌波形较低的旁瓣电平的特性,充分利用双混沌信号设计的频谱特性和失配滤波器时频自由度来调整脉冲压缩后信号的能量分布。仿真结果表明,所设计的混沌波形具有比较好的距离分辨率,并且经失配滤波器脉冲压缩后的近主瓣区的旁瓣电平达到较低水平,对检测距离相近情况下的弱目标具有一定意义。
