衛(wèi)星導(dǎo)航系統(tǒng)電離層閃爍檢測與弱化關(guān)鍵技術(shù)研究
發(fā)布時間：2018-08-24 07:51
【摘要】：空間電離層引起的信號延遲和閃爍導(dǎo)致的信號異常變化,是影響衛(wèi)星導(dǎo)航系統(tǒng)建設(shè)最為棘手的誤差之一,也是影響系統(tǒng)連續(xù)性和可靠性的重要因素。如何估計(jì)并修正電離層延遲帶來的測量誤差、削弱電離層閃爍的影響,確保系統(tǒng)的穩(wěn)定運(yùn)行和用戶的使用性能,是衛(wèi)星導(dǎo)航系統(tǒng)建設(shè)中的重大難題,因此研究電離層背景下的導(dǎo)航信號接收技術(shù),具有重要的工程價(jià)值和戰(zhàn)略意義。在這一背景下,論文開展了以下幾個方面的研究工作:(1)針對傳統(tǒng)的利用多頻測量值估計(jì)電離層延遲的方法,不能應(yīng)用于單頻接收機(jī)的問題,結(jié)合下一代衛(wèi)星導(dǎo)航信號采用BOC調(diào)制、具有分裂譜的特點(diǎn),研究提出了基于BOC調(diào)制雙邊帶信號模型的電離層延遲估計(jì)算法。該算法利用傅里葉級數(shù)展開推導(dǎo)了上下邊帶標(biāo)稱頻率處碼相位延遲量和載波相位超前量的表達(dá)式,以及估計(jì)載波頻率0f處電離層延遲及其變化量的方法,并通過平滑算法進(jìn)一步提高了估計(jì)的精度,仿真結(jié)果表明,該方法可有效提高電離層延遲量的估計(jì)精度,以BOC(10,5)、BOC(14,2)、BOC(15,2.5)為例,此方法的最優(yōu)估計(jì)精度較高,分別能達(dá)到1.26m、0.90m和0.84m,遠(yuǎn)遠(yuǎn)高于現(xiàn)有單頻Klobuchar模型的估計(jì)精度。這使得下一代BOC信號的單頻接收機(jī)具有了準(zhǔn)確估計(jì)電離層延遲的能力。(2)針對傳統(tǒng)的電離層閃爍檢測方法需要積累一段時間觀測數(shù)據(jù)、實(shí)時性較低的問題,提出了基于碼環(huán)NCO調(diào)整量的電離層閃爍檢測算法。由于電離層閃爍引發(fā)信號功率快速衰減時,碼環(huán)NCO的調(diào)整量將會超出正常分布的范圍,并出現(xiàn)與電離層閃爍規(guī)律相近的波動,該算法根據(jù)這一特征,通過碼環(huán)NCO調(diào)整量的變化,檢測是否發(fā)生電離層閃爍,并粗略估計(jì)電離層閃爍的強(qiáng)弱。仿真結(jié)果表明,這種方法采用毫秒量級的檢測間隔,在較短時間內(nèi)可進(jìn)行多次檢測,檢測概率顯著提升,相對于單次檢測,多次檢測的檢測概率在弱閃爍條件下提升了4倍,在強(qiáng)閃爍條件下檢測概率提升了8~10倍;該方法以碼環(huán)NCO控制字調(diào)整量作為判決量,可以實(shí)現(xiàn)電離層閃爍在10s內(nèi)的準(zhǔn)確檢測,相對于傳統(tǒng)的事后統(tǒng)計(jì)分析,該方法可以極大提升電離層閃爍檢測的實(shí)時性。(3)針對電離層閃爍會造成衛(wèi)星導(dǎo)航信號快速衰落、嚴(yán)重時導(dǎo)致失鎖,影響監(jiān)測接收機(jī)等系統(tǒng)設(shè)備的連續(xù)性和穩(wěn)定性的問題,首次提出了基于陣列處理技術(shù)減輕電離層閃爍影響的方法。陣列天線接收在指定方向形成高增益波束,提高該方向衛(wèi)星信號的載噪比,可減輕電離層閃爍對接收機(jī)的不利影響。由于電離層閃爍在短時間內(nèi)(ms量級)是強(qiáng)相關(guān)的,而陣元間的傳播時延在亞納秒量級,陣列處理過程可視為分段穩(wěn)定的過程,文中給出了存在電離層閃爍條件下的陣列信號處理模型,進(jìn)一步分析表明對于不存在干擾的情形,基于最大信干噪比準(zhǔn)則得到的權(quán)值與空域匹配濾波器的權(quán)值相同,且最大增益方向信噪比提升與陣元個數(shù)N成正比。此外還提出了基于可用率的電離層閃爍影響減弱評估方法,定義了電離層閃爍情況下的可用率指標(biāo),分別采用單天線軟件接收機(jī)和陣列接收機(jī)對實(shí)際采集的電離層閃爍數(shù)據(jù)進(jìn)行了仿真分析,結(jié)果表明:4元天線陣接收信號載噪比比單天線提高約6d B,7元天線陣接收信號載噪比比單天線提高約8d B,驗(yàn)證了采用天線陣可以提高電離層閃爍情況下的接收信號載噪比,進(jìn)而降低電離層閃爍對信號接收的影響;在載噪比門限33d BHz情況下,在電離層閃爍較小(閃爍指數(shù)S4=0.2)時,接收信號載噪比及可用率受影響較小;在電離層閃爍較嚴(yán)重(閃爍指數(shù)S4=1.2)時,接收信號載噪比及可用率將顯著下降,而采用天線陣波束形成技術(shù)可以顯著改善接收信號載噪比,可用率可改善39%,驗(yàn)證了天線陣波束形成對電離層閃爍影響的改善效果。(4)針對傳統(tǒng)基于星歷參數(shù)的衛(wèi)星來波方向估計(jì)方法精度差的問題,提出了一種相關(guān)前空間相關(guān)的波束跟蹤改進(jìn)算法�，F(xiàn)有的相關(guān)后空間相關(guān)跟蹤算法存在碼剝離的資源消耗與陣元個數(shù)呈正比的缺點(diǎn),文中提出了一種將空間相關(guān)環(huán)節(jié)置于碼剝離模塊之前,使得不論陣元個數(shù)是多少,都只需要三組碼剝離模塊,隨著陣元個數(shù)的增加,這種處理的優(yōu)勢會更加明顯。在陣列與衛(wèi)星信號的相對來波方向慢變時且碼環(huán)和載波環(huán)穩(wěn)定跟蹤的條件下,本文提出的算法與相關(guān)后波束跟蹤算法是等價(jià)的,文中在數(shù)學(xué)上給出了嚴(yán)格證明。進(jìn)一步的仿真分析表明,新算法可以實(shí)現(xiàn)波束的快速準(zhǔn)確收斂,對衛(wèi)星來波方向?qū)崿F(xiàn)高精度估計(jì),且載噪比提升約6d B,從而實(shí)現(xiàn)信號來波方向的穩(wěn)定跟蹤和信號功率增強(qiáng),有效降低電離層閃爍的影響,也可進(jìn)一步推廣至各類弱信號導(dǎo)航下的應(yīng)用。(5)針對在評估電離層閃爍對幾何精度因子和系統(tǒng)可用性影響方面,缺乏定量分析和統(tǒng)計(jì)方法的問題,提出了基于空時二維的電離層閃爍影響評估方法,研究了以GDOP值惡化因子、可用性等級、閃爍影響惡劣函數(shù)等作為參量的評估準(zhǔn)則,有效評估了電離層閃爍對幾何精度因子和系統(tǒng)可用性的影響。相對于分析GDOP的絕對值變化,采用GDOP值惡化因子的評估方法,能更直觀地反映出電離層閃爍前后GDOP值的相對變化。基于閃爍影響惡劣函數(shù)以及空時二維的可用性評估可知,電離層閃爍影響是一種區(qū)域效應(yīng),一般集中在閃爍中心所對應(yīng)的投影區(qū)域,影響系統(tǒng)可用性的量級在4210~10--,不會對衛(wèi)星導(dǎo)航系統(tǒng)造成較大范圍的影響。論文研究成果已應(yīng)用于我國北斗衛(wèi)星導(dǎo)航系統(tǒng)的總體論證以及地面設(shè)備研制等項(xiàng)目中。
[Abstract]:Signal anomaly caused by ionospheric delay and scintillation is one of the most difficult errors affecting the construction of satellite navigation system, and also an important factor affecting the continuity and reliability of the system. Operational performance and user performance are important problems in the construction of satellite navigation system. Therefore, it is of great engineering value and strategic significance to study the reception technology of navigation signal in ionospheric background. The method of layer delay can not be applied to single-frequency receiver. Considering that the next generation satellite navigation signals are modulated by BOC and have the characteristics of splitting spectrum, an algorithm of ionospheric delay estimation based on BOC modulated bilateral-band signal model is proposed. The expressions of delay and carrier phase lead, and the method of estimating ionospheric delay and its variation at carrier frequency 0f are given. The estimation accuracy is further improved by smoothing algorithm. The simulation results show that the method can effectively improve the estimation accuracy of ionospheric delay. Taking BOC (10,5), BOC (14,2) and BOC (15,2.5) as examples, this method can improve the estimation accuracy of ionospheric delay. The optimal estimation accuracy is 1.26m, 0.90M and 0.84m, respectively, which is much higher than that of the existing single-frequency Klobuchar model. This makes the single-frequency receiver of the next generation BOC signal have the ability to accurately estimate the ionospheric delay. (2) The traditional ionospheric scintillation detection methods need to accumulate some time observation data, real-time performance. A new ionospheric scintillation detection algorithm based on the adjustment of code-loop NCO is proposed to detect the ionospheric scintillation. When the ionospheric scintillation causes the signal power to decay rapidly, the adjustment of code-loop NCO will exceed the normal distribution and the fluctuation of the ionospheric scintillation will occur. According to this characteristic, the algorithm changes the adjustment of code-loop NCO. The simulation results show that this method can detect many times in a short time by using the detection interval of milliseconds, and the detection probability is significantly increased. Compared with single detection, the detection probability of multiple detection is increased by four times under weak flicker condition, and the detection probability of multiple detection is enhanced under strong flicker condition. The detection probability of ionospheric scintillation is increased by 8-10 times under the condition of scintillation. The method can detect the ionospheric scintillation accurately within 10 seconds by using NCO control word adjustment as the decision variable. Compared with the traditional post-event statistical analysis, this method can greatly improve the real-time performance of ionospheric scintillation detection. (3) For ionospheric scintillation will cause satellite navigation information. A method based on array processing technology to reduce the ionospheric scintillation effect is proposed for the first time. The array antenna receives a high gain beam in the specified direction, and improves the carrier-to-noise ratio of the satellite signal in this direction, which can reduce the ionospheric scintillation effect. The disadvantage of scintillation on the receiver is that the ionospheric scintillation is strongly correlated in a short time (ms order) and the propagation delay between the elements is in sub-nanosecond order. The array processing can be regarded as a piecewise stable process. A signal processing model of the array in the presence of ionospheric scintillation is presented. Further analysis shows that the array is non-existent. In the case of interference, the weights based on the criterion of maximum signal-to-interference-to-noise ratio are the same as those of space-domain matched filters, and the enhancement of maximum gain-to-direction signal-to-noise ratio is proportional to the number of elements N. In addition, an assessment method of ionospheric scintillation mitigation based on availability is proposed, and the availability index in the case of ionospheric scintillation is defined. The results show that the carrier-to-noise ratio of the received signal of the 4-element antenna array is 6 d B higher than that of the single antenna, and the carrier-to-noise ratio of the received signal of the 7-element antenna array is about 8 d B higher than that of the single antenna. It is verified that the ionospheric scintillation can be improved by using the antenna array. The carrier-to-noise ratio (CNR) of the received signal in the case of small ionospheric scintillation (scintillation index S4 = 0.2) is less affected when the CNR threshold is 33d BHz; the CNR and availability of the received signal are less affected when the scintillation index S4 = 1.2 is serious (scintillation index S4 = 1.2). The effect of antenna array beamforming on ionospheric scintillation is validated. (4) To solve the problem of poor accuracy of traditional ephemeris-based satellite DOA estimation methods, a correlation front space is proposed. The existing correlated post-spatial correlation tracking algorithm has the disadvantage that the resource consumption of code stripping is directly proportional to the number of array elements. In this paper, a new method is proposed to put the spatial correlation link before the code stripping module, so that no matter how many array elements are, only three groups of code stripping modules are needed. When the relative direction of the array and the satellite signal is slowly changing and the code loop and the carrier loop are stable, the algorithm proposed in this paper is equivalent to the correlated post-beam tracking algorithm, which is proved mathematically rigorously. Further simulation analysis shows that the new algorithm can be realized. The fast and accurate convergence of beam can estimate the direction of arrival of satellite with high accuracy, and the carrier-to-noise ratio can be increased by 6 d B, so that the stable tracking of the direction of arrival of signal and the enhancement of signal power can be realized, and the influence of ionospheric scintillation can be effectively reduced. It can also be further extended to the application of weak signal navigation. (5) Aiming at the evaluation of ionospheric scintillation pairs. In the aspect of geometric accuracy factor and system availability, the problem of lacking quantitative analysis and statistical method is presented. A method of evaluating ionospheric scintillation impact based on space-time two-dimensional is proposed. The evaluation criteria with deterioration factor of GDOP value, usability level and bad function of scintillation effect as parameters are studied. The ionospheric scintillation effect on geometry is effectively evaluated. Compared with the absolute value of GDOP, the relative change of GDOP value before and after ionospheric scintillation can be reflected more intuitively by the evaluation method of GDOP value deterioration factor. The results of this paper have been applied to the general demonstration of Beidou satellite navigation system and the development of ground equipment in China.
【學(xué)位授予單位】：國防科學(xué)技術(shù)大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2014
【分類號】：TN967.1
本文編號：2200129
[Abstract]:Signal anomaly caused by ionospheric delay and scintillation is one of the most difficult errors affecting the construction of satellite navigation system, and also an important factor affecting the continuity and reliability of the system. Operational performance and user performance are important problems in the construction of satellite navigation system. Therefore, it is of great engineering value and strategic significance to study the reception technology of navigation signal in ionospheric background. The method of layer delay can not be applied to single-frequency receiver. Considering that the next generation satellite navigation signals are modulated by BOC and have the characteristics of splitting spectrum, an algorithm of ionospheric delay estimation based on BOC modulated bilateral-band signal model is proposed. The expressions of delay and carrier phase lead, and the method of estimating ionospheric delay and its variation at carrier frequency 0f are given. The estimation accuracy is further improved by smoothing algorithm. The simulation results show that the method can effectively improve the estimation accuracy of ionospheric delay. Taking BOC (10,5), BOC (14,2) and BOC (15,2.5) as examples, this method can improve the estimation accuracy of ionospheric delay. The optimal estimation accuracy is 1.26m, 0.90M and 0.84m, respectively, which is much higher than that of the existing single-frequency Klobuchar model. This makes the single-frequency receiver of the next generation BOC signal have the ability to accurately estimate the ionospheric delay. (2) The traditional ionospheric scintillation detection methods need to accumulate some time observation data, real-time performance. A new ionospheric scintillation detection algorithm based on the adjustment of code-loop NCO is proposed to detect the ionospheric scintillation. When the ionospheric scintillation causes the signal power to decay rapidly, the adjustment of code-loop NCO will exceed the normal distribution and the fluctuation of the ionospheric scintillation will occur. According to this characteristic, the algorithm changes the adjustment of code-loop NCO. The simulation results show that this method can detect many times in a short time by using the detection interval of milliseconds, and the detection probability is significantly increased. Compared with single detection, the detection probability of multiple detection is increased by four times under weak flicker condition, and the detection probability of multiple detection is enhanced under strong flicker condition. The detection probability of ionospheric scintillation is increased by 8-10 times under the condition of scintillation. The method can detect the ionospheric scintillation accurately within 10 seconds by using NCO control word adjustment as the decision variable. Compared with the traditional post-event statistical analysis, this method can greatly improve the real-time performance of ionospheric scintillation detection. (3) For ionospheric scintillation will cause satellite navigation information. A method based on array processing technology to reduce the ionospheric scintillation effect is proposed for the first time. The array antenna receives a high gain beam in the specified direction, and improves the carrier-to-noise ratio of the satellite signal in this direction, which can reduce the ionospheric scintillation effect. The disadvantage of scintillation on the receiver is that the ionospheric scintillation is strongly correlated in a short time (ms order) and the propagation delay between the elements is in sub-nanosecond order. The array processing can be regarded as a piecewise stable process. A signal processing model of the array in the presence of ionospheric scintillation is presented. Further analysis shows that the array is non-existent. In the case of interference, the weights based on the criterion of maximum signal-to-interference-to-noise ratio are the same as those of space-domain matched filters, and the enhancement of maximum gain-to-direction signal-to-noise ratio is proportional to the number of elements N. In addition, an assessment method of ionospheric scintillation mitigation based on availability is proposed, and the availability index in the case of ionospheric scintillation is defined. The results show that the carrier-to-noise ratio of the received signal of the 4-element antenna array is 6 d B higher than that of the single antenna, and the carrier-to-noise ratio of the received signal of the 7-element antenna array is about 8 d B higher than that of the single antenna. It is verified that the ionospheric scintillation can be improved by using the antenna array. The carrier-to-noise ratio (CNR) of the received signal in the case of small ionospheric scintillation (scintillation index S4 = 0.2) is less affected when the CNR threshold is 33d BHz; the CNR and availability of the received signal are less affected when the scintillation index S4 = 1.2 is serious (scintillation index S4 = 1.2). The effect of antenna array beamforming on ionospheric scintillation is validated. (4) To solve the problem of poor accuracy of traditional ephemeris-based satellite DOA estimation methods, a correlation front space is proposed. The existing correlated post-spatial correlation tracking algorithm has the disadvantage that the resource consumption of code stripping is directly proportional to the number of array elements. In this paper, a new method is proposed to put the spatial correlation link before the code stripping module, so that no matter how many array elements are, only three groups of code stripping modules are needed. When the relative direction of the array and the satellite signal is slowly changing and the code loop and the carrier loop are stable, the algorithm proposed in this paper is equivalent to the correlated post-beam tracking algorithm, which is proved mathematically rigorously. Further simulation analysis shows that the new algorithm can be realized. The fast and accurate convergence of beam can estimate the direction of arrival of satellite with high accuracy, and the carrier-to-noise ratio can be increased by 6 d B, so that the stable tracking of the direction of arrival of signal and the enhancement of signal power can be realized, and the influence of ionospheric scintillation can be effectively reduced. It can also be further extended to the application of weak signal navigation. (5) Aiming at the evaluation of ionospheric scintillation pairs. In the aspect of geometric accuracy factor and system availability, the problem of lacking quantitative analysis and statistical method is presented. A method of evaluating ionospheric scintillation impact based on space-time two-dimensional is proposed. The evaluation criteria with deterioration factor of GDOP value, usability level and bad function of scintillation effect as parameters are studied. The ionospheric scintillation effect on geometry is effectively evaluated. Compared with the absolute value of GDOP, the relative change of GDOP value before and after ionospheric scintillation can be reflected more intuitively by the evaluation method of GDOP value deterioration factor. The results of this paper have been applied to the general demonstration of Beidou satellite navigation system and the development of ground equipment in China.
【學(xué)位授予單位】：國防科學(xué)技術(shù)大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2014
【分類號】：TN967.1
【參考文獻(xiàn)】
相關(guān)期刊論文 前1條
1 王曉明;殷耀國;楊自明;;全球?qū)Ш叫l(wèi)星系統(tǒng)的現(xiàn)代化進(jìn)展[J];全球定位系統(tǒng);2006年04期
，本文編號：2200129
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