GPS軟件接收機(jī)捕獲算法研究
發(fā)布時(shí)間：2018-12-28 17:13
【摘要】：近年來,伴隨著導(dǎo)航定位技術(shù)的不斷發(fā)展,全球衛(wèi)星導(dǎo)航系統(tǒng)(Global Navigation Satellite System, GNSS)無論在軍事領(lǐng)域還是民用方面都得到了迅速而廣泛的應(yīng)用,如交通運(yùn)輸、氣象預(yù)報(bào)、社會治安、自然災(zāi)害救助、個人移動電話定位等目前,世界上已有的衛(wèi)星導(dǎo)航系統(tǒng)有美國的GPS、俄羅斯的GLONASS、中國的北斗系統(tǒng)以及歐洲的伽利略導(dǎo)航系統(tǒng)(Galileo)。隨著技術(shù)的不斷革新,傳統(tǒng)的硬件接收機(jī)已經(jīng)無法滿足人們的需求,兼容性、靈活性更強(qiáng)的軟件接收機(jī)在微處理器制造工藝和技術(shù)的支持下成為未來的趨勢。本文重點(diǎn)研究GPS軟件接收機(jī)捕獲階段的問題。 軟件接收機(jī)要求能夠?qū)邮盏降男盘栠M(jìn)行模擬下變頻、A/D采樣、偽碼同步等實(shí)時(shí)處理。其中偽碼同步又包括捕獲和跟蹤兩部分,而實(shí)現(xiàn)同步首先必須實(shí)現(xiàn)同步捕獲(粗同步)。捕獲階段通常要求接收到的偽碼與本地偽碼對齊在某一范圍內(nèi),一旦實(shí)現(xiàn)同步捕獲,就可以通過鎖相環(huán)(PLL)來實(shí)現(xiàn)偽碼的跟蹤過程。若捕獲階段能將本地偽碼與接收端偽碼相位誤差確定在半個碼片之內(nèi),跟蹤階段將很快鎖定偽碼相位；反之,將耗費(fèi)大量的時(shí)間來實(shí)現(xiàn)同步跟蹤。同理,載波頻率的捕獲也直接影響到載波頻率跟蹤階段時(shí)間長短。因此,捕獲算法的設(shè)計(jì)是軟件接收機(jī)設(shè)計(jì)中的關(guān)鍵問題。 本課題重點(diǎn)研究GPS軟件接收機(jī)的直接序列擴(kuò)頻偽碼捕獲問題,并從數(shù)字化處理、捕獲算法研究、捕獲電路的優(yōu)化幾個方面進(jìn)行了研究設(shè)計(jì)。 首先,論文介紹了GNSS的基本發(fā)展情況及GPS系統(tǒng)所采用的直接序列擴(kuò)頻通信原理,研究了GPS信號構(gòu)成、信號的產(chǎn)生及特性,闡述了軟件接收機(jī)各組成部分,從結(jié)構(gòu)、功能等方面對比硬件接收機(jī)與軟件接收機(jī)。 其次,分析捕獲原理,重點(diǎn)闡述了常用的三種捕獲算法,即滑動相關(guān)捕獲、并行頻率捕獲及匹配濾波器捕獲,并從算法的運(yùn)算量、復(fù)雜程度、硬件實(shí)現(xiàn)上進(jìn)行對比,分析利弊,總結(jié)影響捕獲的三個重要因素,即衛(wèi)星運(yùn)動產(chǎn)生的多普勒效應(yīng)、搜索信號時(shí)采用的所搜步長以及捕獲數(shù)據(jù)的長度。并提出適合本文捕獲研究的信號檢測、判決方法、數(shù)字下變頻模塊等。 最后,根據(jù)上文對常用捕獲方法的分析,提出改進(jìn)FFT快速捕獲方法。本文對C/A碼的碼相位并行搜索,對多普勒頻移實(shí)施串行搜索,大大縮減搜索空間。采用FFT算法并行完成接收信號與本地偽碼的相關(guān)運(yùn)算,并在使用FFT運(yùn)算過程中,利用圓周相關(guān)運(yùn)算,減少FFT運(yùn)算次數(shù),從而減少計(jì)算量提高捕獲速度。然后利用仿真分析,與傳統(tǒng)算法進(jìn)行對比。
[Abstract]:In recent years, with the continuous development of navigation and positioning technology, the global satellite navigation system (Global Navigation Satellite System, GNSS) has been rapidly and widely used in both military and civil fields, such as transportation, weather forecasting, social security. Natural disaster relief, personal mobile phone positioning and so on. At present, the existing satellite navigation systems in the world include the GPS, of the United States, the GLONASS, of Russia, the Beidou system of China, and the Galileo navigation system (Galileo). Of Europe. With the continuous innovation of technology, the traditional hardware receiver has been unable to meet the needs of people. The software receiver with more compatibility and flexibility has become a trend in the future with the support of microprocessor manufacturing process and technology. This paper focuses on the acquisition phase of GPS software receiver. The software receiver is required to process the received signals in real time, such as analog downconversion, A / D sampling, pseudo code synchronization and so on. The pseudo-code synchronization includes capture and tracking, and synchronization must be realized first (coarse synchronization). The acquisition phase usually requires that the received pseudo-code is aligned with the local pseudo-code in a certain range. Once synchronous acquisition is realized, the pseudo-code tracking process can be realized by phase-locked loop (PLL). If the acquisition phase can determine the phase error between the local pseudo code and the receiver pseudo code within half a chip, the tracking phase will quickly lock the pseudo code phase; conversely, it will take a lot of time to realize synchronous tracking. In the same way, the acquisition of carrier frequency also directly affects the duration of carrier frequency tracking phase. Therefore, the design of acquisition algorithm is a key problem in software receiver design. This paper focuses on the acquisition of direct sequence spread spectrum pseudo-code for GPS software receiver, and designs and researches from several aspects, such as digital processing, acquisition algorithm and the optimization of acquisition circuit. Firstly, the paper introduces the basic development of GNSS and the principle of direct sequence spread spectrum communication used in GPS system, studies the structure of GPS signal, the generation and characteristics of GPS signal, and expounds the components of software receiver. The function compares the hardware receiver with the software receiver. Secondly, the principle of acquisition is analyzed, and three common acquisition algorithms, namely sliding correlation acquisition, parallel frequency acquisition and matched filter acquisition, are described. The advantages and disadvantages are compared from the calculation, complexity and hardware implementation of the algorithm. Three important factors affecting capture are summarized, which are Doppler effect caused by satellite motion, search step size used in searching signal and length of captured data. The signal detection, decision method, digital downconversion module and so on are proposed. Finally, according to the analysis of common acquisition methods above, an improved FFT fast capture method is proposed. In this paper, the code phase parallel search of C / A code and the serial search of Doppler frequency shift are carried out, which greatly reduces the search space. The FFT algorithm is used to perform the correlation operation between the received signal and the local pseudo code in parallel. In the process of using FFT, the circular correlation operation is used to reduce the number of FFT operations, thus reducing the amount of computation to improve the acquisition speed. Then the simulation analysis is used to compare with the traditional algorithm.
【學(xué)位授予單位】：太原理工大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2014
【分類號】：P228.4
本文編號：2394217
[Abstract]:In recent years, with the continuous development of navigation and positioning technology, the global satellite navigation system (Global Navigation Satellite System, GNSS) has been rapidly and widely used in both military and civil fields, such as transportation, weather forecasting, social security. Natural disaster relief, personal mobile phone positioning and so on. At present, the existing satellite navigation systems in the world include the GPS, of the United States, the GLONASS, of Russia, the Beidou system of China, and the Galileo navigation system (Galileo). Of Europe. With the continuous innovation of technology, the traditional hardware receiver has been unable to meet the needs of people. The software receiver with more compatibility and flexibility has become a trend in the future with the support of microprocessor manufacturing process and technology. This paper focuses on the acquisition phase of GPS software receiver. The software receiver is required to process the received signals in real time, such as analog downconversion, A / D sampling, pseudo code synchronization and so on. The pseudo-code synchronization includes capture and tracking, and synchronization must be realized first (coarse synchronization). The acquisition phase usually requires that the received pseudo-code is aligned with the local pseudo-code in a certain range. Once synchronous acquisition is realized, the pseudo-code tracking process can be realized by phase-locked loop (PLL). If the acquisition phase can determine the phase error between the local pseudo code and the receiver pseudo code within half a chip, the tracking phase will quickly lock the pseudo code phase; conversely, it will take a lot of time to realize synchronous tracking. In the same way, the acquisition of carrier frequency also directly affects the duration of carrier frequency tracking phase. Therefore, the design of acquisition algorithm is a key problem in software receiver design. This paper focuses on the acquisition of direct sequence spread spectrum pseudo-code for GPS software receiver, and designs and researches from several aspects, such as digital processing, acquisition algorithm and the optimization of acquisition circuit. Firstly, the paper introduces the basic development of GNSS and the principle of direct sequence spread spectrum communication used in GPS system, studies the structure of GPS signal, the generation and characteristics of GPS signal, and expounds the components of software receiver. The function compares the hardware receiver with the software receiver. Secondly, the principle of acquisition is analyzed, and three common acquisition algorithms, namely sliding correlation acquisition, parallel frequency acquisition and matched filter acquisition, are described. The advantages and disadvantages are compared from the calculation, complexity and hardware implementation of the algorithm. Three important factors affecting capture are summarized, which are Doppler effect caused by satellite motion, search step size used in searching signal and length of captured data. The signal detection, decision method, digital downconversion module and so on are proposed. Finally, according to the analysis of common acquisition methods above, an improved FFT fast capture method is proposed. In this paper, the code phase parallel search of C / A code and the serial search of Doppler frequency shift are carried out, which greatly reduces the search space. The FFT algorithm is used to perform the correlation operation between the received signal and the local pseudo code in parallel. In the process of using FFT, the circular correlation operation is used to reduce the number of FFT operations, thus reducing the amount of computation to improve the acquisition speed. Then the simulation analysis is used to compare with the traditional algorithm.
【學(xué)位授予單位】：太原理工大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2014
【分類號】：P228.4
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