【作者】 李杨；

【导师】 席晓莉；

【作者基本信息】 西安理工大学 ， 通信与信息系统， 2008， 硕士

【摘要】 GPS射频前端和GPS信号捕获方法在GPS接收机中占有重要的地位,前者的性能优劣直接影响着GPS接收机的接收灵敏度以及后继信号处理部分的性能。后者的性能决定着接收机截获有用信号的能力。因此,本文的主要目的在于对GPS射频前端和GPS信号捕获方法的研究。其中对GPS信号捕获方法的研究主要分为两个方面,即高动态环境下的GPS信号捕获和低信噪比环境下的GPS信号捕获。首先,本文在研究GPS基本原理和射频电路设计基本原理的基础上,探讨了GPS射频前端的设计问题,应用Zarlink公司的GP2010芯片设计出了符合要求的GPS射频前端。其次,本文以传统捕获方法为依托,重点对能满足高动态GPS信号快速捕获要求的基于码相位的FFT捕获方法和基于载波的FFT捕获方法进行了研究。研究表明:前一种方法能够在搜索一个频率单元的同时完成对所有码相位点的搜索,其速度远优于传统的滑动相关捕获方法。后一种方法能够在搜索一个码相位单元的基础上完成对整个多普勒频率的搜索,并且其频率搜索范围大,硬件易于实现。最后,本文对低信噪比环境下的GPS信号捕获技术进行了研究。通过对相干积分和非相干积分算法的研究和实验性能仿真,表征出了这两种算法分别存在的问题:比特翻转和平方损耗。最后,重点介绍了一种差分相干方法,实验仿真说明该方法能够消除上面的缺点,性能远优于相干积分和非相干积分方法,非常适合低信噪比环境下的GPS信号捕获。与此同时,通过对捕获门限的研究,特别对自适应门限中的噪声功率估计方法的研究,提出了三种能有效估计噪声功率的方法。为了提高捕获的检测概率,同时对唐搜索检测器和N中取M搜索检测器的性能进行评估,本文推导了检测器的总虚警概率,总检测概率和平均驻留时间的计算公式。通过数值验证讨论了检测器各参数作用及对捕获性能的影响。其研究结果对实际检测器参数确定具有一定的指导作用。更多还原

【Abstract】 GPS RF front end end and GPS signal acquisition method are very important in GPS receiver.The performance of the former directly affect on GPS receiver sensitivity and signal processing.The performance of the later determine the receiver capability of useful signal capture. So this paper is mainly purpose to study GPS RF Front and GPS signal acquisition method.Firstly, based on studying the basic knowledge of GPS and RF circuit design, this paper discusses the method of GPS RF front design and how to apply Zarlink GP2010 to design it.Secondly, this paper study FFT acquisition method respectively based on carrier wave and code phase.The results show that FFT acquisition method based on code phase can search all code phase cells at searching one doppler cell and FFT acquisition method based on carrier wave can search all doppler cells at searching one code phase cell, having large frequency range and hardware is realized easily.Then the GPS signal acquisition technique under low SNR environment is studied. By reaserching and simulating coherent integration and non-coherent integration, this paper shows that respective disadvantage of them.Finally, differentially coherent integration method is introduced emphatically. The simulation results prove that this method is very suitable for GPS signal acquisition under low SNR environment because it can eliminate the shortcoming of above methods and its performance is far better than them.At the same time, this paper put forward three method of noise power estimaton by acquisition thresholds study, especially noise power estimation study in adaptive threshold. And eventually put In order to increase the detection probability of acquisition, and evaluate the performance of the Tong detector and M of N detector, this paper deduces theoretical formulas for the overall probability of false alarms, the overall probability of detection, and the mean number of dwell times. The function of detector parameters and acquisition performance are demonstrated by numerical simulations.The results contribute to how to confirm detector parameters.更多还原