本文關(guān)鍵詞： GPS 弱信號捕獲 單元概率 系統(tǒng)概率 混合峰均比 FPGA　出處：《電子科技大學(xué)》2013年碩士論文　論文類型：學(xué)位論文

【摘要】：作為為近年來全球發(fā)展最快的信息產(chǎn)業(yè)之一，以GPS為代表的衛(wèi)星導(dǎo)航產(chǎn)業(yè)在我們的日常生活中發(fā)揮著越來越重要的作用。但是在城市，森林，，山區(qū)等環(huán)境下，遮擋、多徑和干擾等現(xiàn)象較嚴(yán)重，這會造成信號的衰弱和退化，現(xiàn)有的普通捕獲技術(shù)就不能夠滿足捕獲低信噪比條件下GPS衛(wèi)星信號的需要。因此如何在微弱信號條件下實(shí)現(xiàn)信號的捕獲成為人們研究的一個(gè)熱點(diǎn)，本文就是主要針對這個(gè)問題進(jìn)行的。 論文首先介紹了GPS信號的基本結(jié)構(gòu)，討論了信號的功率和多普勒頻移特性，構(gòu)建了GPS中頻信號模型。接著討論了GPS信號捕獲的基本原理和兩種常規(guī)的捕獲算法：串行捕獲算法和并行捕獲算法，并對這兩種算法進(jìn)行了計(jì)算機(jī)仿真。 其次，論文研究了三種適用于弱信號條件下的捕獲算法：相干積累、非相干積累和差分相干積累。并對相干積累和非相干積累算法捕獲檢測量的統(tǒng)計(jì)特性、門限設(shè)置以及算法的性能進(jìn)行了分析，得到了適用于單個(gè)搜索單元格的單元概率，并進(jìn)行了MATLAB仿真。 在單元概率的基礎(chǔ)上，論文重點(diǎn)研究了一種具有恒虛警特性的檢測算法：混合峰均比算法，主要從單元概率和系統(tǒng)概率兩個(gè)方面進(jìn)行了對這種算法進(jìn)行了討論。詳細(xì)的理論分析和蒙特卡洛仿真表明，相較于傳統(tǒng)的最大峰均比算法，混合峰均比算法在相近的系統(tǒng)概率條件下能夠節(jié)省大約一半的捕獲搜索運(yùn)算量。 最后，文章選取了基于FFT的并行捕獲算法進(jìn)行了FPGA實(shí)現(xiàn)，并行捕獲算法能夠通過一次計(jì)算得到一個(gè)多普勒頻率上所有碼相位的相關(guān)值，大大提升了捕獲速度。論文從工程實(shí)現(xiàn)角度詳細(xì)的給出了并行捕獲算法中各個(gè)模塊的實(shí)現(xiàn)原理和實(shí)現(xiàn)流程圖，在ISE軟件開發(fā)環(huán)境下，利用Verilog HDL硬件描述語對算法進(jìn)行了實(shí)現(xiàn)。首先仿真數(shù)據(jù)和開發(fā)板采集數(shù)據(jù)對程序進(jìn)行了功能測試，隨后進(jìn)行了程序的外場實(shí)驗(yàn)測試，實(shí)驗(yàn)結(jié)果表明該程序能夠很好的捕獲到GPS衛(wèi)星。
[Abstract]:As one of the fastest growing information industries in the world in recent years, the satellite navigation industry represented by GPS plays a more and more important role in our daily life. But in cities, forests. In mountainous environment, occlusion, multipath and interference are more serious, which will lead to signal debilitating and degradation. The existing common acquisition technology can not meet the need of capturing GPS satellite signals under low SNR. Therefore, how to achieve signal acquisition under weak signal conditions has become a hot topic. This article is mainly aimed at this problem. Firstly, the basic structure of GPS signal is introduced, and the power and Doppler frequency shift characteristics of the signal are discussed. Then the basic principle of GPS signal acquisition and two conventional acquisition algorithms: serial acquisition algorithm and parallel acquisition algorithm are discussed. The two algorithms are simulated by computer. Secondly, we study three acquisition algorithms for weak signal: coherent integration, incoherent integration and differential coherent integration, and measure the statistical characteristics of coherent and incoherent integration algorithms. The threshold setting and the performance of the algorithm are analyzed, the cell probability suitable for a single search cell is obtained, and the MATLAB simulation is carried out. On the basis of the unit probability, this paper focuses on a CFAR detection algorithm: hybrid peak-to-average ratio (PAPR) algorithm. This algorithm is mainly discussed from the aspects of unit probability and system probability. The detailed theoretical analysis and Monte Carlo simulation show that compared with the traditional maximum peak-to-average ratio algorithm. The hybrid peak-to-average ratio algorithm can save about half of the acquisition search operation under the condition of similar system probability. Finally, the parallel acquisition algorithm based on FFT is implemented by FPGA. The parallel acquisition algorithm can get the correlation value of all the code phases in a Doppler frequency. From the point of view of engineering implementation, the paper gives the realization principle and flow chart of each module in parallel acquisition algorithm, under the environment of ISE software development. The algorithm is implemented by using Verilog HDL hardware description language. Firstly, the simulation data and the data collected by the development board are used to test the function of the program, and then the external field test of the program is carried out. Experimental results show that the program can capture GPS satellite well.
【學(xué)位授予單位】：電子科技大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2013
【分類號】：P228.4

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