Pseudorange bias arises from non-ideal characteristics of satellite navigation signals. It manifests as deviations in pseudorange measurement constants, which vary across receivers due to differences in their technical states. It is one of the error sources that have not been effectively corrected in the current high-precision applications of Global Navigation Satellite System (GNSS). This paper studies the pseudorange bias characteristics of the B1I signal in BeiDou Satellite Navigation System (BDS). We analyze the impact of the pseudorange bias on positioning accuracy and propose an improved pseudorange double-difference positioning algorithm considering the pseudorange bias. Through comparative experiments, we evaluate the positioning performance before and after the correction of pseudorange bias at different receiver collocated scenarios. Experimental results demonstrate significant accuracy improvements: post-correction positioning errors are reduced to 0.34 m (E), 0.85 m (N), 0.76 m (U), and 1.17 m (3D), achieving relative enhancements of 22.6%, 43.49%, 21.55%, and 35.59% respectively.

全球定位系统三代首星观测结果显示其星座图具有非恒包络特性,目前国内对非恒包络信号的研究较少,其优势未被充分利用在卫星导航信号设计中.为研究非恒包络信号经过通道失真后的性能,仿真生成恒包络信号和非恒包络信号,构建传输通道相位失真模型,将仿真信号通过失真模型后进行信号质量评估分析,并给出实测信号结果,以进行验证.研究结果表明,在相位失真的影响下,非恒包络信号的测距性能优于恒包络信号.

More and more researches have focused on many aspects of Signal Quality Monitoring (SQM) algorithms which have advanced significantly over these years. However, traditional methods could disclose only the partial aspects of signal quality, little has been done on the comprehensive analysis of different parameters that could together reflect the whole characteristics of signal quality. In this paper, we provided a new method for synthetic power spectrum deviation evaluating, and the analysis parameters related to signal power, waveform, frequency spectrum and correlation curve were further improved based on the traditional methods. The evaluating methods of repairing capability, which is unique for BDS-3, and signal polarization mode were proposed and suggested to be added to SQM algorithms. Based on this, we presented a comprehensive analysis of SQM algorithms. Finally, based on the latest data collected by the 40-m large-aperture antenna at the Haoping Radio Observation from May to September of 2020, the initial signal quality analysis of the new-generation BDS-3 navigation signals for all the thirty in-orbit satellites were given. Results showed that compared with the traditional signal quality assessment system, the satellite signal quality assessment system presented in this paper can fully reflect the merits and disadvantages of satellite navigation signals. Research results can further complement the existing signal quality evaluation system, and provide guide reference for BDS and other GNSS satellite in signal performance testing at various stages.

At present, most satellite navigation systems use constant envelope multiplexed signals, in order to reduce the non-linear influence of the power amplifier as much as possible. However, the actual signal transmission channel cannot be purely ideal. Various amplitude-frequency or phase-frequency distortions that may occur will affect the signal envelope characteristics and ranging performance, resulting in a certain difference between the actual signal received by the user and its theoretical design. Research has shown that the performance of the constant envelope signal after passing through the non-ideal channel may not be better than the corresponding non-constant envelope signal. In order to fully understand the specific effects of various non-ideal characteristics of the channel on the non-constant envelope signal and to judge under which non-ideal characteristics the non-constant envelope signal can show better performance, so as to provide new ideas for the design of navigation signals. This article first studies the non-ideal characteristics of the satellite signal transmission channel and establishes five channel distortion models. The BDS-3 B1 constant envelope and non-constant envelope simulation ideal signals are used as the research signals of this article, use the software receiver to evaluate the signal quality of the ideal signal after the distortion model, and use the evaluation index S-curve zero-crossing deviation to express the signal's ranging performance. Finally, the quantitative analysis and comparison of the ranging performance of different envelope signals under the influence of various distortions are realized. The results show that: Inaddition to amplitude ripple distortion, non-constant envelope signals show better ranging performance overall under the same distortion conditions. The research results of this paper have certain reference value for signal design and signal quality evaluation.

北斗三号全球卫星导航系统正式开通,面对空间电磁环境日趋复杂,地面接收信号功率微弱等问题,强干扰下的B2新信号,对信号质量提出新的挑战及更高的要求.对此,建立了 B2信号及窄带干扰信号模型,仿真分析窄带干扰信号在不同中频、带宽、干信比条件下对信号功率谱偏差、相关损耗、S曲线过零点偏差的影响,并用实测信号进行验证.研究结果表明,窄带干扰信号参数变化对信号质量影响较大,干扰环境恶劣时,信号质量明显变差,导致伪距测量误差较大,影响用户定位精度.研究成果可为干扰监测评估及信号质量评估提供参考依据.

随着人们对卫星导航系统定位精度需求的不断提升,近年来伪距偏差问题越来越受到广泛关注.然而截至目前,国内外专家学者对北斗系统的伪距偏差问题研究甚少.本文首先深入分析了北斗系统的伪距偏差产生根源,在此基础上对伪距偏差随接收机参数设置变化的关系进行详细阐述.然后基于昊平观测站的40m大口径天线采集的各颗北斗卫星下行信号数据,利用软件接收机遍历并分析了在不同接收机带宽、不同相关器间隔情况下,以及不同卫星仰角情况下北斗各颗卫星的B1 I和B3 I信号伪距偏差测量结果.最后根据北斗伪距偏差的特点,首次给出了我国北斗接收机参数设置建议.研究结果表明:在一定的接收机参数设置范围内,本文提出的方法可以将北斗伪距偏差降低到20cm以内.本文的研究成果不仅能够进一步促进广大专家学者对我国北斗伪距偏差的深入了解及广泛关注,同时还能促进我国BDS(BeiDou Navigation Satellite System)及其他GNSS(Global Navigation Satellite System)系统接口控制文件的进一步完善.

The B1C signal of Beidou-3 satellite navigation system adopts data and pilot separation to realize the transmission of message information and ranging functions. The traditional tracking method uses separate data to demodulate the message information, which doesn't fully utilize the signal energy and data-pilot phase relationship, resulting in low tracking accuracy. In order to demodulate the navigation message information more accurately, based on the phase relationship between the data channel and the pilot channel, this paper introduces the tracking strategy of "data + pilot" joints in loop tracking, and proposes three joint methods with different complexity, including "correlator output amplitude superposition", "discriminator output linear union" and "loop filter output linear union". The tracking accuracy of pseudo-code tracking loop and carrier tracking loop under different joint modes is theoretically analyzed, and the applicability of joint tracking in different scenarios is given. Finally, the measured data based on different satellites shows that the higher the inter-code consistency between the data and the pilot, the more obvious the improvement of joint tracking is. The 'correlator output amplitude superposition' method performs the high tracking accuracy and the simplest structure under higher SNR conditions. Under lower SNR conditions, the combination of "code loop filter output linear union + carrier loop discriminator output linear union" shows the highest tracking accuracy and the lowest tracking threshold. Although the loop filter combination increases the loop complexity, it adapts to a wider scene.

为了评估GPS L1频点信号体制转换前后的空间信号质量,基于高增益天线接收系统采集数据,对相干自适应副载波调制(CASM)调制和QPSK调制信号质量进行对比分析.首先,简要介绍CASM调制模型,利用波形匹配技术求解L1频点授权信号伪码序列.其次,基于星座图分布和极大似然估计分别解决出QPSK和CASM调制信号分量功率分配难题.最后定量地利用相关特性参数中的S曲线过零点偏差(SCB)和相关损失(CL)对比分析L1频点信号体制转换前后各信号分量空间信号质量.该文结果可为不同信号体制下空间信号质量评估对比提供参考.

The E1A signal of Galileo system provides high-precision location information service for authorized users. The confidentiality of codes and the auto-correlation multi-peaks of high-order Binary Offset Carrier lead to the lack of relevant research on the quality assessment of E1A signal in the real environment. In this paper, two kinds of high-order BOC tracking algorithms including Bump-Jump and Double Estimator (DET) Technical are studied, then their principles how to eliminate the correlation curve multi-peaks are introduced and compared about advantages and disadvantages. Based on DET, the E1A tracking loop is initialized by using the E1B signal’s carrier information, and then the spreading code modulated message symbol is accurately recovered by waveform-matching method, so the tracking problem of the E1A actual signal is solved. Based on the tracking information of E1A signal, we perform the evaluation of S-Curve Bias (SCB) and correlation loss, and compared those with E1B signal. The results show that the E1A signal correlation loss is greater than the E1B signal, and within 0.15 chip correlator spacing, both SCB are within 0.1 ns. The results have verified the effectiveness of the assessment method of E1A signal quality, as an important reference for improving signal analysis and assessment of GNSS.

Galileo系统在E1频点采用Interplex调制方式播发导航信号,由于缺乏E1信号功率分配和伪码序列等先验信息,一般的研究人员只能开展有限的信号质量特性研究.针对该问题,提出一套基于高增益天线的空间信号质量评估方法,实现了E1授权信号的解析,完善了E1信号评估体系.运用相关功率法来解决信号分量功率比问题,采用跟踪结果解决相位偏差估计问题,提出加权组合平均和码相位平均相结合的新型时域波形分离方法,克服了电文和码多普勒对时域波形特性评估的影响,采用S曲线过零点偏差(S-curve offset Biases,SCB)等参数进行信号测距偏差定量评估.通过该方法对Galileo GSAT-0214卫星进行了评估,结果显示:该卫星E1各信号分量SCB小于0.2ns,测距性能优异,其复用效率达到了97.8％,优于GPS L1信号和北斗三号系统(BDS-3)B1信号.

To validate the new system design and the new technology of the third-generation BDS (BeiDou-3), five non-GEO experimental satellites were launched during 2015 and 2016. In addition to the B1I and B3I signals that have been emitted by BeiDou-2, three newly designed civil signals (B1C, B2a, and B2b) were first transmitted by these satellites and are planned to be partly applied to the official BeiDou-3 satellites. In this study, the signature of elevation-dependent systematic biases in code measurements, which are commonly observed from BeiDou-2 satellites, was investigated for the three new civil signals based on observations collected using different types of receivers at different locations. Our results show that the RMS of multipath combination residuals of the new civil signal B1C was statistically larger than those of B2a and B2b signals. This indicates that B1C tends to be more seriously affected by multipath effects than B2a and B2b. Furthermore, the station elevation-dependent and satellite nadir- and azimuth-dependent multipath signatures were analyzed in detail. The results show that elevation-dependent variations in code measurements of B1I and B3I signals still exist for BeiDou-2 satellites, including the latest IGSO-6 (C13) launched in 2016. Based on different receivers which are equipped with all-in-view antennas, these types of code biases seem to be absent in the legacy B1C, B2a, and B2b frequency bands for BeiDou-3 in-orbit validation satellites. However, benefited from multipath-free conditions, results from a 40-m dish antenna reveal that the satellite-induced code pseudorange variations still exist in the bands of B1C, B2a, and B2b of BeiDou-3 in-orbit validation satellites, although their variation ranges are only at a level of approximately 0.1 m.

Due to the distortions of the broadcasted satellite signals and the inconsistencies of parameter settings for different receivers, the single difference or double difference of pseudo-ranges between two receivers are different for two pair of different receivers. Bias inconsistencies will lead to adverse effects for pseudo-range-based positioning applications. Pseudo-range biases can also hinder carrier-phase ambiguity resolution. However, fewer articles deal with pseudo-range biases for BeiDou navigation satellite System (BDS). In order to mitigate the impact of biases on BDS to the greatest extent, the generation mechanisms and characteristics of pseudo-range biases are studied in detail firstly. Then based on this, experimental verification methods are designed using Haoping Radio Observatory (HRO) of Chinese Academy of Sciences to observe BDS signals. Pseudo-range biases of all visible BDS satellites are measured and evaluated with high accuracy, using the 40 meters dish antenna and modern equipment of HRO. Finally, some important parameters of BDS receivers, such as the correlator spacing and front-end bandwidth, are suggested to mitigate the ranging errors and positioning errors result from pseudo-range biases. The achievements of this paper can provide a worthy reference for GNSS signal designers, GNSS monitoring and assessment and GNSS receiver designers.

Due to the non-ideal characteristics of navigation satellite signals, pseudo-range observations of two satellites for the same signal are different in the same receiver, in addition to that, for zero-baseline receivers, pseudo-range observations between different receivers are different even for the same satellite and the same signal. Bias inconsistencies will lead to adverse effects for pseudo-range-based positioning applications and can also hinder carrier-phase ambiguity resolution. However, fewer article deals with the generation mechanisms of pseudo-range biases for BeiDou Navigation Satellite System. In order to mitigate the impact of biases on BDS to the greatest extent, the generation mechanisms and characteristics of pseudo-range biases are studied in detail in the beginning. Then based on this, experimental verification methods are designed using Haoping Radio Observatory (HRO) of Chinese Academy of Sciences to observe BDS signals. Pseudo-range biases of all visible BDS satellites are measured and evaluated with high accuracy thanks to the 40 m dish antenna and modern equipment of HRO. Finally, some important parameters for BDS receivers, such as the correlator spacing and front-end bandwidth, are provided or suggested to mitigate the ranging errors and positioning errors result from pseudo-range biases. The achievements of this paper could be a worthy reference for GNSS signal designers, GNSS monitoring and assessment and GNSS receiver designers.

In allusion to the phenomenon that the multipath value of BeiDou MEO satellite of its regional system varies with the elevation angle of observation station, we designed an in orbit experiment using test satellite of BeiDou global system on the basis of theoretical analysis and ground test. During the in orbit test, we adjusted the attitude of the satellite repeatedly to simulate the different elevation angles of ground station, used narrow beam of large aperture receiving antenna on the ground to suppressed the multipath effect of ground environment, and reduced influence of ionospheric and other space environment by fast attitude adjustment. We implemented in orbit test according to the design and the result is that the influence of the multipath of the new generation test satellite of BeiDou global system on received data of users is less than 0.1 m, which is equivalent to the GPS satellites, and has a great improvement over the MEO satellite of BeiDou regional system.

Satellite navigation signal waveform is the key factor of signal-in-space quality monitoring. This study mainly focuses on signal waveforms analysis for BDS IGSO-6 frequency B1 by using data of big antenna receiving system. Firstly, code phase average method is proposed to get the high SNR signal waveform, and based on this way the standard chip shape correlator is utilized to extract code element chip. Then, theory between correlation function and code chip is constructed and signal edges characters by using code element chip correlation differences are analyzed. Finally, digital distortions of all BDS satellites are calculated and assessed in detail through signal waveform in time domain.

The quality of Signal-In-Space (SIS) for Global Navigation Satellite System (GNSS) is directly linked to users' Positioning, Velocity and Timing (PVT) service. Limited to the insensitivity of authorized signals, the pseudo codes can not be obtained, so it is difficult to assess the authorized signal quality. This paper mainly focus on analyzing the Coherent Adaptive Subcarrier Modulation (CASM) signal on L1 frequency points for GPS BIIF-5 satellite and the code sequences of P(Y) and M signal are resumed by using matched filtering technology. The power distribution of each signal component can be solved through the maximum likelihood estimation theory combined with the signal characteristics. This paper laies special stress on quantitatively analyzing the correlation performance on P(Y) and M signals, including correlation curve, correlation loss and S-curve biases. Based on this complete authorized signals quality assessment method for GPS L1, the research productions can be reference to other satellite navigation systems' authorized signals.

北斗卫星导航系统(BDS)信号均存在细微的标称失真,传统的研究聚焦于单星信号失真,无法从系统上定量测量各信号由于标称失真带来的测距偏差.该文以大口径天线接收系统采集数据结合软件接收机,从时域波形、通道特性和测距偏差上分析北斗系统B1I信号标称失真.首先利用码相位累加平均方法和标准码片相关技术提取信号时域失真细节,并计算各卫星数字失真量.其次,运用最小二乘法估计信号通道特性,对比分析所有卫星信号通道特性;最后以S曲线过零点偏差(S-Curve Bias,SCB)定量分析B1I信号自然测距偏差及最大测距偏差.文章从多维度定量对比研究了北斗系统B1I信号标称失真,给卫星导航空间信号质量评估和接收机设计提供了新的思路.

It is well known that the traditional evil waveform evaluating method for Binary Phase Shift Keying (BPSK) or Quadrature Phase Shift Keying (QPSK) is the 2nd Order Step (2OS) thread model adopted by the International Civilian Aviation Organization (ICAO).Although there are some new methods to evaluate new Global Navigation Satellite Systems (GNSS) signals, they are all for the analysis of the width and amplitude of signal waveforms.No research has been done on waveform symmetry yet.It has been observed through experiments that waveform asymmetry could also result in tracking errors, range biases, and position errors in GNSS receivers.In order to better evaluate the characteristics of most new navigation signals, the mathematical models for GNSS signals are presented and the extended general thread models are provided from the traditional 2OS thread model.A novel Waveform Rising and Falling Edge Symmetry (WRaFES) model determined for evaluating the asymmetry of GNSS signal waveform is proposed and introduced in details, as well as the evaluating method for Binary Offset Carrier (BOC) correlation curves.WRaFES model characteristics are analyzed in details from the aspects of time domain waveform, correlation domain and S curve bias.Finally, taking the first modernized BeiDou Navigation Satellite System (BDS) satellite M1-S B1Cd signal as an example, the thresholds for signal deformation detection and experimental results from these proposed methods are given.Simulation results and test results show that WRaFES model is very effective not only in detecting waveform asymmetry with high accuracy, but also in analyzing the relationship between waveform asymmetry and tracking error.

Satellite navigation analog threat generate unit abnormal will lead to signal distortion, navigation signal analog threat will directly affect the ranging, positioning performance and other user experience. In this paper, the analog threat signal of BDS are researched and analyzed. Firstly, the large-diameter antenna receiving system is used to obtain the off-line satellite navigation signal data. Using the cumulative average method to process the baseband waveforms. Then, the standard chip correlation technique is used to obtain the optimal symbol waveform. Secondly, the optimal symbol is modeled based on the 2OS model to determine the initial value of the sigma (damping factor) and f(d) (damped frequency) of oscillation. The two-dimensional search is used to search sigma and f(d) respectively. The mean of the difference between ideal signal and the real signal waveform are based for the sigma and f(d) of oscillation values. Finally, the simulation and experimental data are used to verify, the estimation method of the analog distortion parameters of the navigation signal and its influence on the ranging performance are given in detail.

With the advent of new global navigation satellite systems (GNSSs) and new signals, GNSS users will rely more on them to obtain higher-accuracy positioning. Evil waveform monitoring and assessment are of great importance for GNSS to achieve its positioning, velocity, and timing service with high accuracy. However, the advent of new navigation signals introduces the necessity to extend the traditional analyzing techniques already accepted for binary phase-shift keying modulation to new techniques. First, the well-known second-order step thread model adopted by the International Civil Aviation Organization is introduced. Then the extended new general thread models are developed for the new binary offset carrier modulated signals. However, no research has been done on navigation signal waveform symmetry yet. Simulation results showed that, waveform asymmetry may also cause tracking errors, range biases, and position errors in GNSS receivers. It is thus imperative that the asymmetry be quantified to enable the design of appropriate error budgets and mitigation strategies for various application fields. A novel evil waveform analysis method, called waveform rising and falling edge symmetry (WRaFES) method, is proposed. Based on this WRaFES method, the correlation metrics are provided to detect asymmetric correlation peaks distorted by received signal asymmetry. Then the statistical properties of the proposed methods are analyzed, and a proper deformation detection threshold is calculated. Finally, both simulation results and experimentally measured results of Beidou navigation satellite system (BDS) M1-S B1Cd signal are given, which show the effectiveness and robustness of the proposed thread models.