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Interfere with the satellite network positioning signal monitoring and

In Electronic Infomation Category: I | on April 27,2011

1990 business since the rapid development of satellite communications, and RF9906 datasheet and floor space, intentional or unintentional interference on the growing threat of the system. According to the European Telecommunications Satellite Organization (EUTELSAT) of the report, each year hundreds of satellite systems will appear interference events. From the practical application of satellite systems view, disturbance events occur. In order to avoid interference, on the one hand, a reasonable division of spatial frequency resources and RF9906 price and effective protection; must also take prompt and RF9906 suppliers and effective measures to monitor the positioning signal interference. The face of an increasing number of interference events, as well as the satellite receiver and a direct attack and interference, must be studied on the satellite and receiver interference monitoring and positioning technology, and interference monitoring and positioning satellite technology is the potential of the trend.

1 Interference Detection and Location

1.1 Interference Monitoring

Routine monitoring and positioning the interference is only a partial system, the interference should establish an integrated monitoring and positioning technology, not only can interfere with satellite signals for monitoring and positioning, they can fulfill the users interference on the ground monitoring and positioning. Interference Detection and Location of equipment onboard equipment, automotive equipment and ground equipment. Interference with monitoring equipment

ground disturbance from the ground monitoring equipment and satellite signal monitoring equipment components. Include: interference with monitoring the DF antenna, directional antenna, interference signal monitoring and receiving module, the satellite signal monitoring and receiving module. Ground disturbance monitoring equipment shown in Figure 1.

Figure 1 Schematic diagram of the ground disturbance monitoring equipment components

Fixed monitoring and vehicle-mounted ground monitoring, the two modes is quite different. Interfere with monitoring of key vehicle components

diagram shown in Figure 2, the vehicle top to install a multi-array element antenna array, each antenna array element of the RF signal down-conversion to IF, then A / D sampling. From the A / D out of the digital signal and then after band pass filtering and downsampling, the final signal through a real-time adaptive digital beamformer. In order to ensure the various azimuth antenna array angular resolution, you can choose circular antenna array, an array element in the center of the circle, and the remaining antenna elements evenly distributed on the circle, in order to ensure the accuracy of DOA estimation, antenna spacing should be as large as possible.

Figure 2 Schematic diagram of monitoring system of vehicle interference

Before the formation of the beam using the antenna channel extracted from the original signal can be estimated interference signal direction of arrival (DOA). Therefore, as long as the estimated interference sources in different locations in the array DOA value, and then by the triangulation method can estimate the location of interference sources.

1.2 interference location technology

Position of interference, interference sources are generally given three-dimensional parameters: azimuth, distance, height above ground.

Positioning technology is currently the main sources of interference include: based on the signal time difference of arrival (TDOA) location technology, the measured time difference location; based on signal arrival (AOA) positioning technology, the finding and location; based on the signal to reach the frequency difference (FDOA) Location technology. Figure 3 shows this very intuitive interference 3 positioning technology and their connection. In specific implementations, often choose a combination of several technologies to each other for better performance. If the combination of TDOA and FDOA, can make up for TDOA interference location of movement time lag. Triangulation intersects with the Combination of Arc, you can effectively overcome the DF system errors and data random error, and achieve high accuracy.

Figure 3 interference location technology classification

2 interfere with satellite signals transmitted Detection and Location

2.1 to face the satellite interference signal based on the Detection and Location

Interference with the ground monitoring and positioning systems, satellite network monitoring and interference signals are two kinds of location technology: Based on the signal time difference of arrival (TDOA) location technology, the measured time difference location; based on signal arrival (AOA) positioning technology, that is, finding and location.

Time difference of arrival (TDOA) location technology is now the source of interference in the civilian satellite communication system applications. Time Difference of Arrival, also known as hyperbolic positioning (side) position, which is reached by processing the signal time difference between the number of receiving stations to determine the target location, the sense of understanding from the geometric equivalent of measuring the orientation from multiple hyperbolic (surface ) to find the intersection. TDOA positioning generally in the same orbit by two satellites complement each other to achieve, in which a satellite is disturbed, the other a secondary satellite is adjacent satellites can be used, as shown in Figure 4.

Figure 4 satellite interference location theory

In three-dimensional space coordinate system, the use of two satellite jamming signal TDOA location method to determine the source of interference is located only a hyperbolic, but can not determine the exact location of point sources of interference, this is the TDOA location ambiguity. In order to accurately measure the spatial location of the source of interference, but measures must be taken to aid measurement. Such as the use to reach the frequency difference (FDOA) measurement information, or using interference method to solve the blurring. In practice, the ground leakage to adjacent satellite interference signal power tends to be very weak compared to the normal received signal level generally low 30 ~ 40 dB, using the traditional signal detection method can not detect, so the ground control station associated with weak signal detection require high sensitivity receive technology, at least more than 60 dB processing gain.

Finding the earliest and the positioning of the positioning of a widely used method. On in the medium and low orbit satellites, thanks to the use of relative motion between the satellite and ground information, to achieve the positioning measurement is relatively easy. However, for satellites in geosynchronous orbit, the continuous measurement of the method no longer apply. Properties with multi-beam satellite antenna to determine the spatial location of the source of interference is the source of satellite interference technology in recent years, a development direction. Japans Communications Research Institute (CRL) researchers Engineering Test Satellite by ETS-VI of the S-band multi-beam phased array antenna interference source localization experiments, the localization ratio of width measurements for the single pulse; the same time they have also studied the used to suppress interference signal adaptive beamforming technology.

Advantage of measuring the time difference positioning satellite system is the normal operation of the impact of small, but it requires two satellite can also receive the interference signal level, otherwise it can not be properly measured interference source location.

Finding no other satellite positioning technology to help, only the use of satellite can be achieved by the interference of the interference position. However, finding the traditional methods (such as maximum signal method, etc.) lower the positioning accuracy of the application limited in scope. To array signal processing based on spatial spectral estimation techniques (such as maximum likelihood estimation, feature decomposition, and entropy spectral estimation, etc.) exceeded the Rayleigh limit, a high estimation accuracy and spatial resolution performance, while more a radiation source positioning. But its position during the search giants computing needs, and the antenna and the antenna pointing error model error on the positioning accuracy greater impact.

2.2 Satellite Interference Detection and Location

Satellite interference location is ground satellite interference location technology in the field of application, but different from the terrestrial interference location technology.

First, the carrier of the different positioning equipment, ground monitoring and positioning system interference can be a vehicle, and it can be fixed station; and interference monitoring and positioning satellite system is limited by the volume, size, weight and power constraints. Secondly, the two different emphases, the impact of multipath interference monitoring and positioning the ground to solve one of the key issues, and interference monitoring and satellite positioning systems do not need to consider. Third, the antenna used in different forms, ground disturbance monitoring and positioning systems typically use non-directional antenna array for direction finding, and interference monitoring and positioning satellite systems are generally multi-beam antenna, the former assumption that the stream of receiving antenna is the amplitude of the signal, which uses the signal in all time around the different angle of incidence on the phase difference caused by the finding, the multi-beam satellite antenna beam generally does not take into account the received signal of the impact phase, it is the use of The magnitude of the received signal beam to measure the different position.

The spatial spectrum estimation based on the principle of advanced measurement technology can effectively solve the dense signal environment, multiple radiation sources in the high-resolution, high-precision measurement to locate the problem.

Multi-beam antenna satellite antenna. Spatial spectrum estimation methods commonly used maximum likelihood estimation, model parameter method and the characteristics of decomposition method. Among them, the MUSIC algorithm to represent the characteristics of decomposition has been made by people from the high degree of attention, spatial spectrum estimation is still representative of mainstream technology development. The theory is based on sample data using the array covariance matrix, in the structure (pseudo) spectral function into the signal subspace and noise subspace concepts, and take advantage of the orthogonality between the radiation source in the direction of arrival ( DOA) estimation. With the conventional beamforming method is different, feature decomposition method can overcome the limits of the antenna Rayleigh limit, to achieve azimuth / elevation angle of the two-dimensional parameter estimation, has a very high estimation accuracy and super-resolution, excellent performance.

3 receiver interference monitoring and ground-positioning technology

Interference on the ground monitoring and positioning the receiver using interference monitoring device for mobile vehicle. Shown in Figure 5, A device to receive interference signals, transmitted to device B, B device only receives interference signal parameter estimation, while also receiving the interference signal A device forwards, and then processed, derived interference source location.

Figure 5 TDOA positioning

Interference on the ground monitoring and positioning the receiver provided that:

interference source is located in the surface, a high degree of neglect; a single interference source; static interference; interference signal modulation, frequency fixed; Monitoring the source of interference and interference between devices without shelter.

3.1 TDOA technology

Workflow: A device 2, B equipment 1. 2 A device will interfere with signals transmitted to B device, the device B by interfering source location solver.

The factors to be considered (reduce errors and improve the positioning accuracy) for the three devices and its own relative position location accuracy.

Positioning equipment: parameter estimation and parameter estimation accuracy; known parameters in the case of calculating the efficiency of interference source location accuracy; A device forward delay estimation accuracy, time accuracy.

3.2 TDOA + FDOA technology

Workflow: A device, B the need for a device. A device will interfere with signals transmitted to the B device. A device B device receives the transmitted interference signal; received direct transmission interference sources of interference signals; then, the B device at a certain speed of movement, the signal processing, by Doppler frequency shift. 3 groups by processing the signal to get the location of interference sources.

Factors to be considered: 3-device position relationship; B equipment, movement speed, direction; 3-device self-location accuracy.

Positioning equipment: parameter estimation and parameter estimation accuracy; known parameters in the case of calculating the efficiency of interference source location accuracy; A device forward delay estimation accuracy; equipment time accuracy; signal is transmitted when the frequency accuracy.

Program for more than 2 positioning equipment installed on ground vehicles to achieve.

3.3 AOA technology

Workflow: A device, B equipment, 1 each. A device will interfere with signals transmitted to the B device. A device B device receives the transmitted interference signal; received direct transmission interference sources of interference signals; and then, through the direction finder (DF) measured the direction of interference sources which, taken two different AOA line intersection to get the source of interference position.

Factors to be considered: the location between two devices as well as their position accuracy. Pointing device: DF DF accuracy, the gain of the antenna pattern parameters such as frequency changes; A kind of equipment forwarding delay estimation accuracy.

4 Conclusion

Interference Detection and Location in signal processing, it can interfere with the signal for the establishment of appropriate models of different types, the introduction of confidence intervals, confidence levels and other parameters, the interference source location to a certain probability limit in a certain area.

Interference source for independent monitoring and rapid positioning, can interfere with the signal source to fight, but need to take proactive measures, such as the user machines, and satellite receivers to adaptive filtering and anti-jamming antenna nulling techniques. Therefore, interference and interference monitoring and location satellite system technology is a very important protection needs in the understanding of disturbance and anti-jamming technology, there are many issues that need further study.

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