北斗导航接收机捕获技术研究与设计

发布时间：2018-05-06 14:43

本文选题：北斗二代卫星导航系统 + 定长相干积分遍历/非遍历　；参考：《厦门大学》2014年硕士论文

【摘要】：随着北斗二代卫星导航系统的成功组网并投入使用,对能够支持北斗二代卫星导航系统的用户端导航定位设备的研发需求也日益迫切。由于北斗二代卫星导航系统的B1信号中引入了二次编码调制技术,在提高互相关性能的同时也给卫星信号的捕获方法带来了挑战,NH码的调制使得每间隔1ms就有可能产生符号位跳变,这就限制了B1信号的相干积分时长,严重影响了北斗二代卫星B1信号的捕获性能,因此本文应用了定长相干积分遍历/非遍历的并行码相位搜索的粗捕获算法,实现了对北斗二代卫星B1信号的长时间相干积分捕获,提高了B1信号的捕获性能。粗捕获得到的载波频率估计精度通常无法满足跟踪环路的要求,需进行精细频率捕获,本文针对B1信号的特点,提出基于频域插值的载波频率估计算法,在粗捕获之后,对B1信号进行精频捕获,改善载波频率估计精度。本文首先对北斗二代卫星B1信号的结构进行分析,针对NH码的自身特点设计了定长相干积分遍历的并行码相位搜索算法,然后对该算法进行了仿真,仿真结果验证了该算法的正确性,在相干积分长度为4ms的情况下,可以捕获载噪比为37dB·Hz的B1信号。接着针对该算法计算量较大的缺点进行了改进,提出了定长相干积分非遍历的并行码相位搜索算法,以牺牲一定的捕获性能为代价减小计算量,并仿真了不同搜索次数算法在最差情况下的捕获性能。其次,粗捕获得到的载波多普勒频率精度较低,需要进行精频捕获,针对B1信号的精频捕获问题,本文提出基于频域插值的载波频率估计算法,并对该算法进行仿真,仿真结果显示该算法成功改善了低信噪比环境下载波多普勒频率的估计精度。本文还使用模拟器产生的B1信号对基于频域插值的载波频率估计算法进行测试,验证该算法对于改善低信噪比环境下载波频率估计精度的有效性。最后本文对于定长相干积分20次搜索遍历/10次搜索非遍历的并行码相位搜索的粗捕获算法在FPGA平台上进行了硬件实现,并使用了三个不同场景的真实北斗二代卫星B1信号进行测试,验证了硬件实现的正确性。
[Abstract]:With the successful networking and application of the Beidou second generation satellite navigation system, the research and development of the user terminal navigation and positioning equipment which can support the Beidou second generation satellite navigation system is becoming more and more urgent. Because of the introduction of quadratic coded modulation technology in the B1 signal of Beidou second generation satellite navigation system, While improving the performance of cross-correlation, it also brings challenges to the acquisition method of satellite signal. The modulation of NH code makes it possible for 1ms to produce symbol bit jump at every interval, which limits the time of coherent integration of B1 signal. The acquisition performance of Beidou second generation satellite B1 signal is seriously affected. In this paper, the coarse acquisition algorithm of parallel code phase search based on constant coherence integral ergodic and non-ergodic is used. The long time coherent integral acquisition of Beidou second generation satellite B1 signal is realized, and the capture performance of B1 signal is improved. The accuracy of carrier frequency estimation from coarse acquisition can not meet the requirements of tracking loop, so fine frequency acquisition is needed. In this paper, a carrier frequency estimation algorithm based on interpolation in frequency domain is proposed, which is based on the characteristics of B1 signal. Precision frequency acquisition of B1 signal is carried out to improve the accuracy of carrier frequency estimation. In this paper, the structure of Beidou second generation satellite B1 signal is analyzed, and the phase search algorithm of parallel code is designed according to the characteristic of NH code, and then the algorithm is simulated. The simulation results show that the algorithm is correct, and the B1 signal with 37dB Hz can be captured when the coherent integral length is 4ms. Then, aiming at the disadvantage of the algorithm, a phase search algorithm of parallel code is proposed, which can reduce the computational complexity at the expense of certain capture performance. The capture performance of different search times is simulated in the worst case. Secondly, the accuracy of carrier Doppler frequency obtained by coarse acquisition is low, so fine frequency acquisition is needed. Aiming at the problem of fine frequency acquisition of B1 signal, a carrier frequency estimation algorithm based on interpolation in frequency domain is proposed in this paper, and the algorithm is simulated. Simulation results show that the proposed algorithm can improve the estimation accuracy of carrier Doppler frequency in low SNR environment. This paper also tests the carrier frequency estimation algorithm based on interpolation in frequency domain by using the B1 signal generated by the simulator to verify the effectiveness of the algorithm in improving the accuracy of carrier frequency estimation in low SNR environment. Finally, the rough acquisition algorithm of parallel code phase search based on FPGA platform is implemented on the platform of FPGA, which has 20 traversal / 10 non-ergodic parallel code phase search algorithms with fixed coherence integral. The true Beidou second generation satellite B1 signal of three different scenarios is used to verify the correctness of the hardware implementation.
【学位授予单位】：厦门大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TN965.5

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