【作者】 周艳玲；

【导师】 胡修林；

【作者基本信息】 华中科技大学 ， 通信与信息系统， 2012， 博士

【摘要】 随着全球导航卫星系统(Global Navigation Satellite System, GNSS)的快速发展，二进制偏移载波调制(Binary Offset Carrier, BOC)信号的无模糊接收和导航信号的码片波形设计成为该领域关注的热点问题。导航信号的自相关函数(Autocorrelation Function,ACF)影响GNSS系统的性能。BOC信号由于其具有分裂式频谱，使其具备相对更好的码跟踪精度，抗多径干扰能力以及与其它导航信号的兼容性；但由于BOC的ACF呈现多峰性使其存在捕获和跟踪模糊问题，减轻或消除BOC信号捕获跟踪中存在的模糊，是有效发挥BOC信号固有的高精度和抗多径优点的前提条件。码片波形决定了导航信号的ACF和功率谱，从而影响到测距精度和抗多径干扰能力，也是导航信号设计的关键部分。本文针对这两个问题取得的主要成果如下：(1).针对余弦相位BOC (Cosine phased BOC, CosBOC)信号提出了一种有效的抑制副峰，减轻模糊的方法。本文基于抵消相关函数副峰的目的设计了本地辅助信号的码片波形，利用该辅助信号与接收的CosBOC信号的互相关函数来抵消本地复现信号与接收的CosBOC信号的相关函数的副峰，获得的捕获函数中仅剩两个正副峰，且主副峰幅度比显著增大，再联合经典峰跳(Bump Jump, BJ)方法来区别主峰与副峰。该方法的捕获概率有所下降，优点是减轻模糊的能力好于单纯使用BJ算法，且调制阶数越大改善程度越明显，对于CosBOC(15,2.5)，在主峰跟踪概率为0.9时，该方法需要的信噪比低于单纯使用BJ算法约4dB；且在多径干扰环境下，该方法的主峰跟踪概率也整体上优于单纯使用BJ方法。(2).提出了一种基于伪相关方法(Pseudo Correlation Function, PCF)的本地参考信号码片波形设计方法，推导出获得的单峰特性的伪相关函数的数学表达式，着重分析了该方法的跟踪和抗多径性能与本地参考波形宽度因子关系。该方法从根本上解决了BOC信号码跟踪模糊问题。随着本地参考信号码片波形的宽度因子增加，跟踪精度也逐步提高；当宽度因子为1，载噪比大于30dB-Hz时，该方法的跟踪精度接近假设无模糊问题时的传统码跟踪方法精度。该方法对于延迟较长的多径信号抑制能力优于传统方法，当多径延迟大于0.3chip时多径误差为零。(3).研究表明SinBOC(1,1)和MBOC(6,1,1/11)信号的ACF与其绝对值的之和可以消除副峰。将传统相干超前减滞后跟踪环路中的相关输出用该相关输出与其绝对值之和来代替，解决了SinBOC(1,1)和MBOC(6,1,1/11)信号的跟踪模糊问题，且由于其保留了原相关函数的尖锐主峰，从而保证了其较好的跟踪精度和抗多径能力，其性能均优于BOC-PRN相干处理方法。(4).根据导航信号的需求，分析了将在时域上集中分布同时在频域上能量最大化集中在某个频段的长椭圆球波函数(Prolate Spheroidal Wave Functions, PSWF)作为一种新的卫星导航信号码片波形的可行性。给出了该码片波形的相关函数和功率谱特征，并对比分析了PSWF码片波形与带限BOC调制码片波形用在卫星导航定位时的码跟踪精度和抗多径干扰性能。结果表明：当码速率一定，且在合适的带宽下，PSWF码片波形具有比带限BOC码片波形好的跟踪性能和抗多径能力。更多还原

【Abstract】 With the advent of the new global navigation satellite system (GNSS), theunambiguous acquisition and tracking for the binary offset carrier modulation (BOC) andthe pulse shape design of the navigation signal are two hot issues.The autocorrelation function (ACF) of navigation signal affects the performance ofthe GNSS system. Due to the split spectrum of BOC signals, they have been proposed toimprove the measurement precision, enhance robustness against multipath and guaranteethe coexistence and compatibility with different systems. However, the autocorrelationfunction (ACF) of the BOC signals has multi peaks which may bring about ambiguity intraditional code tracking loop. Mitigating or eliminating the ambiguity effectively forBOC signals acquisition and tracking is the prerequisite for exerting the inherent highaccuracy and anti-multipath advantages of BOC signals. The pulse shape determines theACF and power spectral density of the navigation signal which affects ranging accuracyand anti-multipath interference performance, so it is also the key part of the system. Maincontents about the two issues are as follows.(1) An effective method of suppressing the sub-peak and mitigating ambiguity isproposed for Cosine phased BOC (CosBOC) signals. One particular symbol of the localauxiliary signal is derived in this thesis. The main idea is to use the cross-correlationfunction of the received cosine-phased BOC signal with the specifically designed localauxiliary signal to counterbalance the undesired side peaks of the received cosine-phasedBOC autocorrelation function, the final correlation function has only two small positiveside peaks and the amplitude ratio of the main and side peak increases significantly, thencombing with the classical Bump Jump (BJ) technique to distinguish the main peak andthe two small residuary peaks effictively. Simulations show that at the cost of somedegradation of detection probability in the acquisition phase the proposed method is betterthan the traditional BJ method in mitigating the ambiguity, as the modulation orderincreases the improvement is more obvious. The SNR of the proposed method atprobability of the main peak tracking as0.9is4dB lower than that of the BJ method.Even under multipath interference the proposed method is also higher in the main peak tracking probability than the BJ method.(2) One kind of sufficient condition of the local reference waveform for the pseudocorrelation function (PCF) method is proposed. The mathematical expressions of the PCFmethod are derived, and the performances when the parameters of the local referencepulse shape are different are analysed. Simulations show that the PCF method isunambiguous, as the width factor of the local reference signal increases the trackingaccuracy gradually increases. The accuracy of the PCF method is close to the traditionalacquisition under the assumption that no false acquisition occurs when the width factor is1and the C/N0is larger than30dB-Hz. And the method is better than the traditionalmethod in mitigating the middle and long multipath interferences, the multipath errorenvelopes are zero when the multipath delay is larger than0.3chip.(3) Research shows that the additions of the ACFs of SinBOC (1,1) orMBOC(6,1,1/11) and the absolute value of their ACFs are unambiguous. An unambiguoustracking technique which substitutes the combination of the correlation outputs and theabsolute value of the correlation outputs for the correlation outputs in the coherentEarly-minus-Late architecture loop is proposed. The technique can completely removesthe side-peaks from the ACF of SinBOC (1,1) and MBOC(6,1,1/11) while still keepingthe sharp main-peak, which maintains the tracking accuracy and anti-multipath propertiesof the BOC modulation. The performances are better than the BOC-PRN coherent method.(4) According to the demand of navigation signal, the thesis analyses thepracticability that the prolate spheroidal wave functions (PSWF) which are concentrated inthe time domain and maximized energy in the specified bandwidth as a new kind ofnavigation signal pulse shape. The ACF and power spectral density of the pulse shape aregiven. Then the navigation performances of the PSWF pulse shape and BOC pulse shapewith the same code rate and bandwidth constraints are compared. The results show thatwithin the appropriate bandwidth the PSWF pulse shape is better than the band-limitedBOC in code tracking precision and anti-multipath interference on the whole.更多还原