Satellite Navigation Receiver Research Articles

Analysis of the approaches to protection against interference of UAV satellite navigation receivers.

The main approaches to the construction of signal receivers of global satellite navigation systems of unmanned aerial vehicles, protected from the influence of artificially created interference, are considered. Such systems are equipped with multi-element phased antenna arrays and devices of controlled reception pattern antenna. In the process of processing the received information signal by the Controlled Reception Pattern Antenna device. the selection of interference and their suppression (compensation) is ensured, which is equivalent to the formation of dips in the spatial pattern of the antenna array at the corners that correspond to the directions of the interference sources. The basic principles of the implementation of the adaptive algorithm for processing the received information signal are given. The design and composition of the navigation receiver of the «Orlan-10» unmanned aerial vehicle equipped with a Controlled Reception Pattern Antenna device is considered. A conclusion was made regarding the fundamental possibility of creating a domestic navigation receiver with a Controlled Reception Pattern Antenna device. In the future, it is envisaged to deploy works on the creation of Controlled Reception Pattern Antenna devices with a greater number of antenna elements and the use of optimization principles of the quantitative composition of adaptation operations, in order to ensure the performance of these devices with a greater number of simultaneously enabled sources of interference and higher levels of their signal power.

An Unassisted Super-Resolution Satellite Navigation Receiver Using GPS L5 Signals

An Unassisted Super-Resolution Satellite Navigation Receiver Using GPS L5 Signals

Adaptive Satellite Navigation Anti-Interference Algorithm Based on Inverse Cosine Function

Contrasting the dilemma that the traditional time-domain least mean square (LMS) algorithm in the existing satellite navigation receiver anti-interference system cannot satisfy the convergence time is short and maintain a low level of steady-state error at the same time, an inverse cosine variable step size LMS algorithm (ICVS-LMS) is proposed. To begin with, the LMS algorithm, with a fixed step size focuses on its effectiveness in attenuating and suppressing interference signals, is analyzed, and then the proposed ICVS-LMS algorithm is analyzed. In conclusion, both the ICVS-LMS algorithm and the traditional algorithm are simulated and compared in terms of their effectiveness in suppressing interference in satellite navigation signals. The experimental results demonstrate that the improved algorithm significantly reduces convergence time while maintaining a small steady-state error. The improved algorithm demonstrates high robustness and an obvious suppression effect on interference signals. The anti-interference performance is 8.41–12.22% higher than that of the proposed algorithm.

Improved path following for autonomous marine vehicles with low-cost heading/course sensors: comparative experiments

By overcoming constraints of low-cost sensors equipped on the autonomous marine vehicle (AMV), the classic path following approaches based on heading autopilot and course autopilot are improved to enhance the following accuracy of AMV, respectively. For the heading autopilot, adaptive line-of-sight (ALOS) is proposed to compensate for the generalized sideslip including the actual sideslip angle and the magnetic compass bias. For the course autopilot, extended Kalman filter (EKF) is employed to fusion the position and yaw angular rate to obtain the more precise and stable course, so as to substitute the unreliable course feedback from the satellite navigation receiver in cases of low speed and non ideal positioning. The performance and characteristics of both improved schemes are summarized through comparative experiments conducted on a low-cost AMV. Compared with the classic path following method, the straight line path following accuracy of the heading autopilot with generalized sideslip compensation and the course autopilot with EKF feedback are improved by 78.3% and 85.8% respectively. The circular path following accuracy are improved by 61.8% and 66.7% respectively. Engineers can choose the path following methods flexibly based on the hardware configuration, working environment and path type of the AMV to improve the following accuracy.

Assisted-GNSS positioning algorithm based on one-way fuzzy time information

In order to solve the problem that the accuracy of approximate position and approximate time information is limited by the traditional auxiliary positioning algorithm, this paper analyzes the problem that the calculation amount may increase and fail when these auxiliary information exceeds the precision requirement range and puts forward a positioning algorithm based on one-way fuzzy time assistance that is suitable for the positioning solution of GNSS satellite navigation receivers under the condition of fuzzy time information, such as the rotation condition. Methods using the reference information in the ephemeris information, the relatively accurate approximate time information can be reasonably searched and verified so as to achieve the effect of obtaining the positioning result with less calculation. The experimental results show that this method can accurately calculate the exact position even if there is an error in the approximate position information under the condition of one-way time assistance, which not only solves the problem that it cannot be positioned under the conditions of rotation but also does not increase the additional calculation amount and has practical engineering value.

Preliminary processing of data from a satellite navigation receiver in the problem of three-dimensional upper ionosphere tomography

Preliminary processing of data from a satellite navigation receiver in the problem of three-dimensional upper ionosphere tomography

Cold-Start Satellite Signal Acquisition Aided by an Antenna Array in the Presence of Outliers

In the cold-start mode, this work addresses the issue of signal acquisition for a satellite navigation receiver aided by an antenna array in the presence of outliers. First, the satellite signals acquisition is formulated as a problem of sparse matrix recovery in terms of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\ell _{2,1}$</tex-math></inline-formula> -norms minimization which encourages row sparsity of signal matrix and effectively suppresses outliers simultaneously. Then, an iterative reweighted framework and the Lagrange multipliers method with complex-valued conjugate gradient descent are employed to find a suitable solution. After that, to accelerate the convergence rate of the mean square error (MSE), an improved <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\ell _{2,1}$</tex-math></inline-formula> -norms cost function with composite regularizers is devised, where several conjugate gradients of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\ell _{2,1}$</tex-math></inline-formula> -norms are derived in detail and convex optimization theory is employed to find the global minimum. At last, actual satellite almanac is downloaded to provide the information of the visible satellites and then numerical results are presented to demonstrate the effectiveness of the proposed methods.

Influence of sweep interference on satellite navigation time-domain anti-jamming

The global navigation satellite system (GNSS), represented by global positioning systems (GPS), is widely used in various civil and military fields and represents an essential basis for space-time information services. However, the radar signals partially overlap with the frequency band of satellite navigation signals, seriously affecting the normal reception of weak satellite navigation signal power. To further improve anti-jamming with sweep interference in the time domain, this paper focuses on the sweep interference scenario, studies the influence of the sweep interference on time-domain-adaptive anti-jamming, and proposes a timing reset based on the adaptive filter. The proposed method can effectively deal with the influence of sweep interference on time-domain-adaptive anti-jamming and can suppress interference and protect signals at the same time. Simulation experiments verify the effectiveness of the anti-jamming method proposed in this paper. Under the typical simulation scenarios, the influence time of the frequency sweep interference on the navigation signal is less than 1 m when the timing reset period is 1 m, which is significantly reduced compared to traditional methods. The proposed anti-jamming method is of great significance for improving the survivability of satellite navigation receivers in sweep interference scenarios.

ИССЛЕДОВАНИЕ ПОМЕХОУСТОЙЧИВОСТИ МУЛЬТИСИСТЕМНОГО GNSS ПРИЕМНИКА

The article presents the results of a study of the noise immunity of the ATGM336H multi-system GNSS receiver to the influence of narrow-band interference at the L1 frequency set for one of the systems (GLONASS or GPS). The review of existing works on the study of noise immunity of satellite navigation receivers is carried out. The method of conducting experiments is presented. The simulator CH-3803M was used as a signal source from navigation satellites. The analysis of the results obtained during the experiments for the formulation of narrow-band interference of various capacities via GPS and GLONASS channels is carried out.

Sidelobes Suppression for Time Domain Anti-Jamming of Satellite Navigation Receivers

The global satellite navigation system represented by global position systems (GPS) has been widely used in civil and military fields, and has become an important cornerstone of space-time information services. However, the frequency band of satellite navigation signals is open, and the frequency points overlap with some radars and communication systems, which brings challenges to the application of satellite navigation. Time-domain adaptive filtering technology is a typical anti-jamming method which can suppress the narrow-band interference faced by satellite navigation. However, in the process of suppressing narrow-band interference, the navigation signal will be distorted, which is mainly reflected in the distortion of the spectrum of the navigation signal, which will lead to the enhancement of the side lobes in the correlation function. In this paper, we focus on time-domain adaptive anti-jamming, study the mechanism of correlation function sidelobes lift caused by narrow-band interference suppression, and propose a correlation function sidelobes suppression method based on time-domain adaptive anti-jamming, which can be realized without losing anti-jamming performance. The simulation experiment verifies the validity of the mechanism analysis of the sidelobes lift of the correlation function and the effectiveness of the proposed method. The analysis results and the proposed method are of great significance, which is reflected in the improvement of the anti-jamming performance and acquisition performance of satellite navigation receivers.

A Distortionless Anti-Jamming Method Based on STAP for GNSS Receiver

Global Navigation Satellite System (GNSS) receivers often realize anti-jamming capabilities by combining array antennas with space-time adaptive processing (STAP). Unfortunately, in suppressing the interference, basic STAP degrades the GNSS signal. For one thing, additional carrier phase errors and code phase errors to the GNSS signal are introduced; for another, the shape of the cross-correlation function (CCF) will be distorted by STAP, introducing tracking errors when the receiver is in tracking mode. Both of them will eventually cause additional Pseudo-Range (PR) bias, and these problems prevent STAP from being directly applied to high-precision satellite navigation receivers. The paper proposes a novel anti-jamming method based on STAP that solves the above problems. First, the proposed method constructs a symmetric STAP by constraining the STAP coefficients. Subsequently, with the information of the steering vector, a compensation FIR filter is cascaded after the symmetric STAP. This approach ensures that the proposed method introduces only a fixed offset to the code phase and carrier phase, and the order of the STAP completely determines the offset, which can be compensated during PR measurements. Meanwhile, the proposed method maintains the symmetry of the CCF, and the receiver can accurately track the carrier phase and code phase in tracking mode. The effectiveness of the proposed method is validated through simulations, which suggest that, in the worst case, our method does not increase carrier and code phase errors and tracking error at the expense of only a 2.86dB drop in interference suppression performance.

Robust Anti-Jamming Algorithm Based on Transmit/Receive Time-Sharing Technology

Transmit/Receive (T/R) time-sharing is a critical technology to ensure accurate space–time reference information of navigation signals, which solves the problem of co-channel interference between receiver and transmitter. The rapid development of the electronic information industry has led to severe frequency band conflicts between different electronic systems. Satellite navigation receivers must take measures to suppress interference to eliminate the effects of narrowband interference, mainly unintentional interference. Time-domain anti-jamming is widely used in navigation receivers for its simple and easy advantages in ensuring the validity and stability of navigation data. However, because the satellite-ground link receivers adopt transmit/receive time-sharing technology to realize the bidirectional measurement and communication function of the link, the stability of the data solution is greatly affected by anti-interference in the time domain. The anti-jamming filter of the traditional navigation receiver usually re-converges from the initial state in each signal-receiving time slot, which leads to the receiver losing high volume data due to repeated convergence. This paper proposes a robust time-domain anti-jamming technology based on transmit/receive time-sharing technology. The continuity and stability of the interference signal are used to obtain the preliminary information of the periodic transceiver. The results show that robust anti-jamming technology based on a T/R time-sharing navigation signal can effectively improve the carrier-to-noise ratio loss and data loss caused by traditional time-domain anti-jamming technology, reduce the convergence time to nanosecond level, and has bright prospects in the future application of other navigation systems.

A Novel Design of Flat-Top Beamforming Anti-Multipath Antenna

This article discusses a novel design method of wide-beam circular polarization array antenna for satellite navigation. For special applications such as satellite navigation guiding aircraft landing, high-performance ground reference station antennas are required. In the system of satellite navigation guiding aircraft landing, the antenna of satellite navigation receiver needs to have the following radiation characteristics: the shape of antenna pattern is close to an ideal hemisphere, the upper half of space has uniform right-hand circular polarization gain, and the beam has the characteristic of sharp cutoff below 5 degrees of elevation. Whether the GNSS reference station antenna can have a wider beam circular polarization characteristic to receive more navigation satellites signal; whether it can suppress the multipath effect to a greater extent to reduce the multipath error; and whether it can work in a wider frequency band, so that several major satellite navigation systems work together, the above factors directly affect the satellite navigation and positioning accuracy of the entire system. The beam of this antenna has the following feature: sharp cutoff near the horizon for multipath mitigation at low elevation angles. Comprehensive design thereby accelerates system design. It owns wide beam, good circular polarization characteristics, low elevation angle sharp cutoff, and ultralow sidelobe radiation characteristics that achieve the purpose of receiving satellite navigation signal and multipath. The low sidelobe characteristic of the antenna is beneficial to suppress multipath effect. According to the theoretical knowledge of the symmetrical dipole and the four-arm helical antenna, the simple structure of the symmetrical element is fully utilized, and the printed balun easily realizes the dual-frequency operation of the antenna. Combined with the wide-beam circular polarization characteristic of the four-arm helical antenna structure, the shaped beam array antenna is designed. The wide-beam circularly polarized antenna unit not only covers the frequency band of the satellite navigation system but also satisfies the system performance and key feature requirements of the array antenna for the unit; that is, it satisfies the wide-beam circular polarization characteristics of the upper half space. According to the linear array basic theory and array antenna synthesis theory, Woodward Lawson sampling synthesis algorithm is used to synthesize the array amplitude and phase weights corresponding to the specific antenna pattern required for the Ground-Based Augmentation System (GBAS) engineering. The shaped beam array antenna consists of 21 units, of which 11 antenna units are directly fed, and the feeding ports of the rest are dummy ports. It is an equally spaced array antenna. The spacing between antenna units is close to half wavelength. They are fed according to the value corresponding to the excitation function. The array antenna is simulated by HFSS (High-Frequency Structure Simulator). Compared with traditional satellite navigation antennas, the antenna in this paper has excellent front-to-rear ratio and flat-top beam pattern. The results show that the wide-beam circularly polarized array antenna meets the engineering requirements of GBAS applications and lays the solid foundation for GBAS engineering applications.

Approximate Position Estimation Method of Weak-Signal Receiver of Global Navigation Satellite Systems Assisted by Barometric Altimeter

The satellite navigation receiver works in an environment, where the received signal is very weak. Sometimes, frame synchronization is impossible, for the antenna rotates with the flight carrier, and occlusions exist in the environment. After losing look, it is necessary to positioning reacquired signals. Rapid positioning can be completed without frame synchronization, utilizing auxiliary positioning algorithms like A-GPS. If the carrier is highly dynamic, however, the computing load of reacquired signal positioning would be too high, owing to the extreme fuzziness of the approximate position. Therefore, the application of auxiliary positioning algorithms is premised on the acquisition of the approximate position information, when frame synchronization is not possible. This paper proposes a method for estimating the approximate position of a satellite navigation receiver without frame synchronization: The approximate position is quickly obtained by measuring the elevation with a barometer, and searching under a user-defined “geocenter-satellite” coordinate system. Simulation results show that, the proposed algorithm could successfully compute the approximate position, when the barometric altimeter measures elevation with an accuracy within 1.8km, and when the coordinate system is established based on satellites with a long distance and a low angle of elevation, under the condition of global navigation satellite system (GNSS) constellation.

Research on Detection Technology of Spoofing under the Mixed Narrowband and Spoofing Interference

The global navigation satellite system has achieved great success in the civil and military fields and is an important resource for space-time information services. However, spoof interference has always been one of the main threats to the application security of satellite navigation receivers. In order to further improve the application security of satellite navigation receivers, this paper focuses on the application scenarios where narrowband and spoofing interference exist at the same time, studies the problem of spoofing interference detection under mixed interference conditions, then proposes a spoofing interference detection method based on the tracking loop identification curve. This method can effectively deal with the detection of spoofing interference under the conditions of narrowband interference and, at the same time, it can effectively detect the spoofing interference of gradual deviation. Simulation experiments verify the effectiveness of the spoofing interference detection method, based on the tracking loop discrimination curve. In typical jamming and spoofing scenarios, when the spoofing signal is about 7.5 m away from the real signal, the method used in this paper can achieve effective detection. The proposed detection method is of great significance for improving the anti-spoofing capability of satellite navigation receivers.

Distortionless 1/2 Overlap Windowing in Frequency Domain Anti-Jamming of Satellite Navigation Receivers

Frequency-domain anti-jamming technology is a common anti-jamming method for satellite navigation receivers. 1/2 overlapping windowing can effectively solve the spectrum leakage in the frequency domain conversion process, but the traditional window function will cause the loss of signal energy. This paper proposes a window function design method with no loss of signal energy, which can effectively solve the signal energy loss caused by the window function. The feasibility of the proposed method is theoretically deduced, and the effectiveness of the proposed method is verified by simulation and measured data. Compared with the traditional window function, the signal-to-noise ratio improvement of the method proposed in this paper is better than 0.5 dB. The frequency domain anti-jamming processing is optimized, the signal-to-noise ratio loss caused by the anti-jamming processing is reduced, and the anti-jamming performance is indirectly improved. This plays an important role in the performance optimization of satellite navigation system links.

Design of Ionospheric TEC Gradient Anomaly Detection Platform Based on GNSS

Abstract Ionospheric anomalies can seriously threaten important flight phases such as approach and landing, so accurate real-time monitoring is necessary. In this paper, an ionospheric anomaly gradient detection platform is designed for satellite navigation receiver. Based on GNSS observation data, the spatial gradient of ionospheric vertical total electron content is calculated, and anomaly ionospheric gradient is detected using generalized likelihood ratio test method. To verify the correctness of detection results, rate of TEC change index is also calculated for comparison. Simulation results show that the platform can detect ionospheric anomaly gradient state fast and accurately, and the proposed approach can used by GNSS receivers to detect ionospheric anomaly.

Design of GNSS Receiver Autonomous Integrity Monitoring Platform under Ionospheric Scintillation

Abstract How to evaluate the impact of ionospheric scintillation on the availability of RAIM technology is a key problem to be solved in the field of global satellite navigation system (GNSS) security applications. Based on the relationship between ionospheric scintillation and satellite navigation signal parameters, a scheme of RAIM technology monitoring platform for satellite navigation receiver under ionospheric scintillation is proposed. Firstly, the phase screen model is used to simulate the GNSS satellite navigation signal affected by ionospheric scintillation. Then, the key module of GNSS receiver autonomous integrity monitoring platform under ionospheric scintillation is designed. Simulation results show that the designed platform can effectively simulate satellite navigation signals under ionospheric scintillation and test the effectiveness of various RAIM technology.

Optimal Order of Time-Domain Adaptive Filter for Anti-Jamming Navigation Receiver

Adaptive filtering algorithms can be used on the time-domain processing of navigation receivers to suppress interference and maintain the navigation and positioning function. The filter length can affect the interference suppression performance and hardware utilization simultaneously. In practical engineering, the filter length is usually set to a large number to guarantee anti-jamming performance, which means a high-performance receiver requires a high-complexity anti-jamming filter. The study aims at solving the problem by presenting a design method for the optimal filter order in the time-domain anti-jamming receiver, with no need for detailed interference information. According to interference bandwidth and jam-to-signal ratio (JSR), the approach designed a band-stop filter by Kaiser window for calculating the optimal filter order to meet interference suppression requirements. The experimental results show that the time-domain filtering processing has achieved good interference suppression performance for engineering requirements with optimal filter order in satellite navigation receivers.

A filter algorithm for receiver tracking loops assisted by inertial information

AbstractIn traditional satellite navigation receivers, the parameters of tracking loop such as loop bandwidth and integration time are usually set in the design of the receivers according to different scenarios. The signal tracking performance is limited in traditional receivers. In addition, when the tracking ability of weak signals is improved by extending the integration time, negative effect of residual frequency error becomes more and more serious with extension of the integration time. To solve these problems, this paper presents out research on receiver tracking algorithms and proposes an optimised tracking algorithm with inertial information. The receiver loop filter is designed based on Kalman filter, reducing the phase jitter caused by thermal noise in the weak signal environment and improving the signal tracking sensitivity. To confirm the feasibility of the proposed algorithm, simulation tests are conducted.