scholarly journals PERFORMANCE OF GNSS CARRIER-TRACKING LOOP BASED ON KALMAN FILTER IN A CHALLENGING ENVIRONMENT

2019 ◽  
Vol XLII-2/W13 ◽  
pp. 1687-1693 ◽  
Author(s):  
Y. Luo ◽  
C. Yu ◽  
J. Li ◽  
N. El-Sheimy
Keyword(s):  
Kalman Filter ◽  
Model Simulation ◽  
Random Noise ◽  
Dynamic Environment ◽  
Satellite System ◽  
Phase Lock Loop ◽  
Integration Time ◽  
Loop Model ◽  
Tracking Loop ◽  
Coherent Integration

<p><strong>Abstract.</strong> The global navigation satellite system (GNSS) recently plays an extremely important role in positioning, navigation, and timing (PNT) applications for the modernized automations and mechanizations, e.g., unmanned aerial vehicles (UAVs), unmanned ground vehicles (UGVs), military aircrafts, etc. Nevertheless, GNSS signals are very vulnerable to the influence of various interferences when they are received on Earth, and the reason why it happens is that the long line-of-sight (LOS) distance between the satellite and the receiver user dramatically reduces the power strength after the signal reaches at the ground. The weak GNSS signal is hard to be handled with traditional phase lock loop (PLL), especially in a dynamic environment. Again, the trade-off among the coherent integration time of tracking loop, received signal power strength, and signal or user receiver dynamics is still a tough and remained problem to be solved. The Kalman filter (KF) is always a promising tool to efficiently decrease the random noise for the tracking process. In our work, we evaluate the performances of the tracking loop modelled with both standard KF and extended Kalman filter (EKF). An adaptive algorithm for the covariance matrix of the process noise is contained in our system to increase the tracking ability in a weak and dynamic environment. Besides, a noise channel is also contained to automatically adjust the priori measurement covariance for the KF tracking loop model. Simulation results demonstrate the performance with the proposed technique.</p>

scholarly journals A Two-Stage Kalman Filter-Based Carrier Tracking Loop for Weak GNSS Signals

Sensors ◽  
2019 ◽  
Vol 19 (6) ◽  
pp. 1369 ◽  
Author(s):  
Yan Cheng ◽  
Qing Chang ◽  
Hao Wang ◽  
Xianxu Li
Keyword(s):  
Kalman Filter ◽  
Satellite System ◽  
Convergence Time ◽  
Integration Time ◽  
Two Stage ◽  
Navigation Data ◽  
Coherent Integration ◽  
Tracking Loops ◽  
Coherent Integration Time ◽  
Global Navigation Satellite

For global navigation satellite system receivers, Kalman filter (KF)-based tracking loops show remarkable advantages in terms of tracking sensitivity and robustness compared with conventional tracking loops. However, to improve the tracking sensitivity further, increasing the coherent integration time is necessary, but it is typically limited by the navigation data bit sign transition. Moreover, for standard KF-based tracking receivers, the KF parameters are initialized by the acquired results. However, especially under weak signal conditions, the acquired results have frequency errors that are too large for KF-based tracking to converge rapidly to a steady state. To solve these problems, a two-stage KF-based tracking architecture is proposed to track weaker signals and achieve faster convergence. In the first stage, coarse tracking refines the acquired results and achieves bit synchronization. Then, in the second stage, fine tracking initializes the KF-based tracking by using the coarse tracking results and extends the coherent integration time without the bit sign transition limitation. This architecture not only utilizes the self-tuning technique of the KF to improve the tracking sensitivity, but also adopts the two-stage to reduce the convergence time of the KF-based tracking. Simulation results demonstrate that the proposed method outperforms conventional tracking techniques in terms of tracking sensitivity. Furthermore, the proposed method is compared with the standard KF-based tracking approach, proving that the proposed method converges more rapidly.

scholarly journals Comparison of the Segmentation Results of Two Carrier Tracking Loop Types and Analysis of Theoretical Influencing Factors

2021 ◽  
Vol 13 (11) ◽  
pp. 2035
Author(s):  
Qian Wang ◽  
Mengyue Han ◽  
Yuanlan Wen ◽  
Min He ◽  
Xiufeng He
Keyword(s):  
Evaluation Method ◽  
Dynamic Balance ◽  
Theoretical Data ◽  
Real Data ◽  
Phase Lock Loop ◽  
Integration Time ◽  
Measuring Error ◽  
Tracking Loop ◽  
Theoretical Level ◽  
Loop Design

This paper proposes an accurate quantitative segmentation method by analyzing the probability distribution of tracking variance and strict derivation based on the tracking loop theory. The segmentation points are taken as characteristics of phase lock loop (PLL) and frequency lock loop (FLL) performances, and the two factors that cause the performance difference are discriminator gain and filtering coefficient, which denote proportional and integration coefficients, respectively. The filtering coefficients lead to a difference of 2.5 dB-Hz between the FLL and PLL. Moreover, through the analysis of the normalized bandwidth and phase margin, it is found that the integration time and bandwidth need a dynamic balance to achieve the best performance. Finally, the simulation results and real data are in good agreement with the theoretical analysis results. The minimum mean error rate of the deviation between the real data and the theoretical data is only 1.8%. In the proposed method, the influence of external hardware factors on the tracking loop is removed, and the loop design factors are modeled directly. Instead of testing the denoising performance based on the ranging and angle measuring error after location calculation, the filter coefficient is proposed to evaluate the processing performance of the tracking loop objectively and directly at the theoretical level, which proposes a new performance evaluation method at the theoretical level. The results presented in this study provide theoretical support for the design of a new-type tracking loop with enhanced performances.

scholarly journals Signal-to-Noise Ratio Analyses of Spaceborne GNSS-Reflectometry from Galileo and BeiDou Satellites

2021 ◽  
Vol 14 (1) ◽  
pp. 35
Author(s):  
Yang Nan ◽  
Shirong Ye ◽  
Jingnan Liu ◽  
Bofeng Guo ◽  
Shuangcheng Zhang ◽  
...  
Keyword(s):  
Global Navigation Satellite System ◽  
Signal To Noise Ratio ◽  
Satellite System ◽  
Integration Time ◽  
Navigation Satellite ◽  
Signal To Noise ◽  
Coherent Integration ◽  
Global Navigation ◽  
Coherent Integration Time ◽  
Global Navigation Satellite

In recent years, Global Navigation Satellite System Reflectometry (GNSS-R) technology has made considerable progress with the increasing of GNSS-R satellites in orbit, the improvements of GNSS-R data processing technology, and the expansion of its geophysical applications. Meanwhile, with the modernization and evolution of GNSS systems, more signal sources and signal modulation modes are available. The effective use of the signals at different frequencies or from new GNSS systems can improve the accuracy, reliability, and resolution of the GNSS-R data products. This paper analyses the signal-to-noise ratio (SNR) of the GNSS-R measurements from Galileo and BeiDou-3 (BDS-3) systems, which is one of the important indicators to measure the quality of GNSS-R data. The multi-GNSS (GPS, Galileo and BDS-3) complex waveform products generated from the raw intermediate frequency data from TechDemoSat-1 (TDS-1) satellite and Cyclone Global Navigation Satellite System (CYGNSS) constellation are used for such analyses. The SNR and normalized SNR (NSNR) of the reflected signals from Galileo and BDS-3 satellites are compared to these from GPS. Preliminary results show that the GNSS-R SNRs from Galileo and BDS-3 are ∼1–2 dB lower than the GNSS-R measurements from GPS, which could be due to the power of the transmitted power and the bandwidth of the receiver. In addition, the effect of coherent integration time on GNSS-R SNR is also assessed for different GNSS signals. It is shown that the SNR of the reflected signals can be improved by using longer coherent integration time (∼0.4–0.8 dB with 2 ms coherent integration and ∼0.6–1.2 dB with 4 ms coherent integration). In addition, it is also shown that the SNR can be improved more efficiently (∼0.2–0.4 dB) for reflected BDS-3 and Galileo signals than for GPS. These results can provide useful references for the design of future spaceborne GNSS-R instrument compatible with reflections from multi-GNSS constellations.

scholarly journals Improvement of Carrier Phase Tracking Based on a Joint Vector Architecture

2017 ◽  
Vol 2017 ◽  
pp. 1-9 ◽  
Author(s):  
Shaohua Chen ◽  
Yang Gao
Keyword(s):  
Carrier Phase ◽  
Satellite System ◽  
Phase Lock Loop ◽  
Tracking Loop ◽  
Phase Measurements ◽  
Phase Tracking ◽  
Cycle Slips ◽  
Carrier Phase Tracking ◽  
The Individual ◽  
Global Navigation Satellite

Carrier phase measurements are essential to high precision positioning. Usually, the carrier phase measurements are generated from the phase lock loop in a conventional Global Navigation Satellite System (GNSS) receiver. However there is a dilemma problem to the design of the loop parameters in a conventional tracking loop. To address this problem and improve the carrier phase tracking sensitivity, a carrier phase tracking method based on a joint vector architecture is proposed. The joint vector architecture contains a common loop based on extended Kalman filter to track the common dynamics of the different channels and the individual loops for each channel to track the satellite specific dynamics. The transfer function model of the proposed architecture is derived. The proposed method and the conventional scalar carrier phase tracking are tested with a high quality simulator. The test results indicate that carrier phase measurements of satellites start to show cycle slips using the proposed method when carrier noise ratio is equal to and below 15 dB-Hz instead of 21 dB-Hz with using the conventional phase tracking loop. Since the joint vector based tracking loops jointly process the signals of all available satellites, the potential interchannel influence between different satellites is also investigated.

scholarly journals Unambiguous Acquisition/Tracking Technique Based on Sub-Correlation Functions for GNSS Sine-BOC Signals

Sensors ◽  
2020 ◽  
Vol 20 (2) ◽  
pp. 485 ◽  
Author(s):  
Fang Hao ◽  
Baoguo Yu ◽  
Xingli Gan ◽  
Ruicai Jia ◽  
Heng Zhang ◽  
...  
Keyword(s):  
Random Noise ◽  
Tracking Error ◽  
Satellite System ◽  
High Order ◽  
Signal Acquisition ◽  
Phase Detection ◽  
Binary Offset Carrier ◽  
Side Peak ◽  
Phase Discrimination ◽  
Coherent Integration

The autocorrelation function (ACF) of the Binary Offset Carrier modulation (BOC) signal for Global Navigation Satellite System (GNSS) has multiple peaks, ambiguity is easily generated during the synchronization of the baseband signal. Some methods have been proposed to remove the ambiguity, but the performance is not suitable for high-order BOC signals or does not maintain narrow correlation characteristics. This paper proposes a sub-function reconstruction synchronization algorithm to solve this problem, of which the key is to design a new local auxiliary code: the local Pseudo-Random Noise (PRN) code is divided into several new codes with different delays. The auxiliary code performs a coherent integration operation with the received signal. Then, a correlation function without any positive side peaks is obtained by multiplying the two correlation results to make the acquisition/tracking completely unambiguous. The paper gives a design scheme of navigation signal acquisition/tracking and deduces the theoretical analysis of detection performance. The phase discrimination function is provided. The performance of the method is analyzed from both theoretical and simulation aspects. Compared with the Binary phase shift keying-like (BPSK-LIKE) method, Subcarrier Phase Cancellation (SCPC) method and the Autocorrelation Side-Peak Cancellation Technique (ASPeCT) method, the proposed method has the best detection probability for the acquisition, which is 0.5 dB-Hz better than ASPeCT. For tracking, the proposed method performs best in terms of phase-detection curve, anti-multipath performance, and anti-noise performance. For high-order BOC signals, the SRSA technique successfully removes the false lock points, and there is only one multipath error envelope, and the code tracking error is almost the same as the ASPeCT method.

Galileo E5 Signal Acquisition using Intermediate Coherent Integration Time

2019 ◽  
Vol 72 (3) ◽  
pp. 555-574
Author(s):  
Jérôme Leclère ◽  
René Landry
Keyword(s):  
Partial Correlation ◽  
Correlation Method ◽  
Satellite System ◽  
Integration Time ◽  
Signal Acquisition ◽  
Coherent Integration ◽  
L5 Signal ◽  
Galileo E5 ◽  
Low Sensitivity ◽  
Global Navigation Satellite

The acquisition of modern Global Navigation Satellite System (GNSS) signals may be difficult due to the presence of a secondary code. Indeed, short coherent integration times should be used without non-coherent integration, which implies a low sensitivity; or long coherent integration times should be used, requiring synchronisation with the secondary code and thus a full correlation, which implies a significant computational burden, especially for signals with long secondary codes such as the Galileo E5 signal. A third option that lies between the previous two is to perform a partial correlation using less than one secondary code period as input, however this is less efficient in terms of complexity than using an entire secondary code period, and the code's autocorrelation properties are completely changed. The authors recently proposed a method based on combining secondary code correlations, allowing the use of intermediate coherent integration times with the possibility to do non-coherent integrations, and the method was successfully applied to the Global Positioning System (GPS) L5 signal. This paper studies the application of the method to the Galileo E5 signal, compares it with the partial correlation method, and discusses the case where less than one secondary code period is used as an input

Kalman filter identification method for micro-vibration transfer paths of satellites

2021 ◽  
pp. 095441002110533
Author(s):  
Yan Shen ◽  
Yang Xu ◽  
Xiaowei Sheng ◽  
Xianbo Yin
Keyword(s):  
Kalman Filter ◽  
Correlation Coefficients ◽  
Vibration Signal ◽  
Satellite System ◽  
Solar Array ◽  
Target Point ◽  
Mechanical Equipment ◽  
Displacement Response ◽  
Transfer Path ◽  
Identification Method

Micro-vibrations on-board a satellite have degrading effects on the performance of certain payloads like observation cameras. The major sources of vibrations include momentum wheels, solar array drives, other rotary mechanical equipment, etc. These vibrations result in loss of the pointing precision and image quality of the payload through intricate transfer paths. To improve the accuracy of a satellite system with many vibration sources and complex transfer paths, it is necessary to determine the main transfer path of vibration. In this study, a path identification method is proposed and applied to the transfer system from the momentum wheel to the camera mount. First, the observer/Kalman filter identification (OKID) algorithm is used to acquire the state-space equation of each path subsystem. Then, the subsystem order is obtained based on the slope of the singular entropy increment. In the next phase, combined with the measured disturbance force of the momentum wheel, the displacement response of the target point is predicted. Finally, the dominant transfer path of vibration is achieved by calculating the vibration contribution of each path to the response point. The results indicate that the dominant transfer path is the axial path of the horizontal momentum wheel, which contributes to the vibration of the camera mount at most. Effective vibration reduction measures should be taken to this path to suppress the vibration signal. In comparing the identified displacement response with the finite element response of the camera mount under different noise conditions, the correlation coefficients are >0.85, which proves the accuracy and anti-noise capability of the identification method.

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