Yangbo Huang

Adaptive wavelet denoising unscented Kalman filter for BeiDou signal carrier tracking under ionospheric scintillation conditions

Abstract. Ionospheric scintillation can cause BeiDou system (BDS) signal amplitude fading and phase variation as the radio frequency (RF) signals pass through the ionosphere. With the accidental, sudden, and regional characteristics of ionospheric scintillation, it is difficult to effectively mitigate the impacts of ionospheric scintillation from a system perspective. To overcome this problem, this work addresses the mitigation of scintillation for the BDS signal. We propose an adaptive wavelet denoising unscented Kalman filter (WDUKF)-based carrier tracking algorithm to mitigate the adverse impacts of ionospheric scintillation. First, as WD can better characterize the nonstationary of signal, the non-Gaussian noise caused by scintillation can be filtered by designing a sliding window-based online WD filter. Second, taking the denoised integrations as an input, we employ the phase lock indicator (PLI)-based adaptive UKF carrier phase estimator to reduce the linearization approximate error of conventional KF-based algorithms. Through adjusting the measurement vector of UKF with different scintillation scenarios adaptively, the divergence problem of UKF can be mitigated. Simulation and real data experimental results demonstrate the validity of the proposed method, especially in the case of 36 dB-Hz in moderate scintillation, the phase jitter and probability of loss-of-lock decrease about 6 deg (40%) and 71%, respectively.

High Accuracy and Real-Time Pseudorange Generation for GNSS Navigation Signal Simulator Based on Hermit Interpolation

Focusing on the issue that the traditional high accuracy pseudo range generation is hard to satisfy the real-time request, a high accuracy real-time pseudo range generation method based on Hermit interpolation was proposed after the performance comparison of different interpolation algorithm. Then, its theoretical accuracy is analyzed and the main influence factors on the pseudo range generation accuracy are simulated. The results indicate that the real-time performance can reach 10 milliseconds on the condition of 1 millimeter accuracy, which can fully satisfy the real-time request of GNSS navigation signal simulator.

Optimal Observation Intervals for Clock Prediction Based on the Mathematical Model Method

In this paper, we derive the optimal observation intervals for the prediction of cesium and hydrogen maser atomic clocks based on the mathematical model method. The theoretical analyses, simulations, and experiments are based on a linear model for cesium clocks and on a quadratic model for hydrogen masers. The results are supported by numerical simulations and experimental measurements. The experimental measurements are the time deviations of the cesium clock Cs2142 and the hydrogen maser Hm4926 at the National Time Service Center of China with respect to International Atomic Time.

Feasibility Analysis of GNSS Multi-constellation Positioning for Lunar Spacecraft

With the development of deep space exploration technology, as the representative project of the Chinese lunar exploration, the possibility of using global navigation satellite system (GNSS) for deep space exploration spacecraft positioning has become a hot issue. Based on the existing GNSS research on high orbital spacecraft positioning, the feasibility of using GNSS multi-constellation for lunar orbit spacecraft positioning is deep analyzed. On condition of signal acquisition’s lowest carrier to noise ratio (CNR) threshold, 21 dB Hz, two cases of signal receiving are analyzed from which GNSS satellite transmitting antenna beam’s main lobe and side lobe. Simulation results show that when only receiving the beam main lobe signal of GNSS transmitting antenna, any single constellation or multi-constellation combination of GNSS cannot satisfy positioning of lunar spacecraft on the lunar revolution orbit for whole period (about 27 days). When signals from the main lobe and side lobe of the GNSS received, three constellations combination or more can satisfy positioning for the whole lunar orbit period. Conclusion is that GNSS multi-constellation combination method is possible to complete the mission of deep space exploration project for lunar spacecraft positioning on the simulated conditions.

A GNSS Space-Time Anti-jamming Algorithm Based on Convex Optimization

Traditional space-time adaptive processing algorithm can not well balance the demands between canceling jams and beam-forming. Aimed at this problem, A new algorithm based on convex optimization and multiple objectives programming is proposed for the designing of space-time filter. Two object functions are defined, and are combined via an object weight coefficient to form a single optimization goal. The relationship between the object weight coefficient and the optimization results is analyzed, and then proposed the criterion for judge the rationality of the object weight coefficient. The method for finding the optimal object weight coefficient is then developed. Results of computer simulation show that: the new method can form wide band main beam for useful signal direction under both strong and weak jams with a more low inserting loss compared with PI method; it overcomes the shortcomings of MSINR method that pass band of equivalent filter for useful signal direction will get narrower when the taps increase; especially when the signal and narrow-band jams come from the same direction the new method can still perform well.

High-Quality BDS Navigation Signal Simulator Based on GPU Optimized Design

High-quality navigation signal simulator plays an important role as the verifying method for the function and capacity of navigation receivers. With the development of GPU, software navigation signal simulator based on CPU + GPU is developing rapidly because it’s easy to transplant, update and maintain. However, current signal generation algorithms are not fully optimized. The generalized signal generation architecture based on GPU is built in this paper, and optimized GPU thread design is obtained by theoretical analysis and testing based on the architecture. The test results prove that the optimized algorithm is able to generate multiple channels of high-dynamic and high-quality GNSS signals. The time consumption is separately 93.6% and 1.73–7.73% less than the two methods before and the optimized capacity does not change while number of signal channels change. The optimized algorithm is already applied in BDS satellite simulator system.

GNSS Spoofing Mitigation Method After Despreading

GNSS spoofing signals have the same signal structure as authentic signals, so it is difficult to mitigate the spoofing in time and frequency domains, and space domain processing has become one of the most powerful methods for spoofing cancelation. But most of the existing spoofing mitigation methods are implemented before signal despreading and their computational complexity is generally low, but their mitigation performance deteriorates seriously as the spoofing power decreases. To solve the problem, a spoofing mitigation method after signal despreading is proposed in this paper. Simulation results show that the proposed method is practicable and outperforms the methods before signal dispreading in a large variation range of spoofing power.

Research on MEMS IMU Aided BeiDou Receiver Carrier Loop Technology

In dynamic scenarios, the loop bandwidth of BeiDou receiver must be sufficiently wide and the integration time should be short to ensure stable tracking. It will introduce too much noise to the tracking loop with the increase of bandwidth and the reduction of integration time, resulting in the loss of lock of BeiDou receiver carrier tracking loop in high dynamic scenarios. Therefore, high dynamic position is hard to be achieved. In this paper, steady tracking performance with auxiliary has been performed under different \( {\text{C}}/{\text{N}}_{0} \) (carrier to noise ratio) and dynamic scenarios, and we propose the range of accuracy of the PLL effectively aided by MEMS IMU under different orders, and then analyze the auxiliary optimal bandwidth under different orders. Simulation results show the improvement of bandwidth with auxiliary under different grades of MEMS IMU and different orders of PLL.

The GPS Spoofing Detection Based on the Joint WSSE of DOA and Pseudorange

With the development of GPS spoofer techniques, spoofing signals can be consistent with the authentic signals on direction of arrival (DOA) or pseudorange. The receiver will not be effective for detecting such spoofing signals, when using traditional spoofing detection method based on either DOA or pseudorange. In order to suppress this problem, a method based on the joint weighted sum of squares of errors (WSSE) of DOA and pseudorange for GPS spoofing detection is introduced. This method uses the carrier-phase difference and pseudorange observations to form two equations simultaneously, and adds the residuals of two equations after normalization. According to the joint WSSE, it can test the DOA and pseudorange of arrival signals at the same time. Because of this, it can greatly improve the adaptability to different spoofing scenarios. This paper also gives the process to identify and eliminate spoofing signals in the received signals. In conclusion, the performance between the method based on the joint WSSE of DOA and pseudorange and the traditional method based alone on DOA or pseudorange is compared. The simulation results show that the proposed method is superior to the traditional way both in the adaptability to different spoofing scenarios and the detection performance.

BeiDou Satellites Assistant Determination by Receiving Other GNSS Downlink Signals

GNSS’s orbit determinations always rely on ground station or intersatellite links (ISL). In the emergency of satellite-to-ground links and ISL break-off, BeiDou navigation satellite system (BDS) satellites cannot determine their orbits. In this paper, we propose to add a spaceborne annular beam antenna for receiving the global positioning system (GPS) and global navigation satellite system (GLONASS) signals; therefore, the BDS satellites may be capable of determining their orbits by GPS/GLONASS signals. Firstly, the spectrum selection, the power isolation, the range of Doppler frequency shift, and changing rate are taken into account for the feasibility. Specifically, the L2 band signals are chosen for receiving and processing in order to prevent the overlapping of the receiving and transmitting signals. Secondly, the minimum number of visible satellites (MNVS), carrier-to-noise ratio (), dilution of precision (GDOP), and geometric distance root-mean-square (gdrms) are evaluated for acquiring the effective receiving antennas’ coverage ranges. Finally, the scheme of deploying 3 receiving antennas is proved to be optimal by analysis and simulations over the middle earth orbit (MEO), geostationary earth orbit (GEO), and the inclined geosynchronous satellite orbit (IGSO). The antennas’ structures and patterns are designed to draw a conclusion that installing GPS and GLONASS receivers on BDS satellites for emergent orbits determination is cost-effective.