Application describes gps signal generator

Application gps signal generator introduces
what GPS Signal Generator?
If you are developing any equipment dependent on GPS satellite signals, etc., you must make sure it can meet its stated performance requirements of the task. But how can you determine that you are ready to meet the needs of real-world equipment put on the market before it? You need to use the GPS signal generator to perform appropriate tests.
Due to the lack of actual sky signal, lab tests they have extreme importance, especially when some of the satellite launch yet. Satellite tracking devices will be the key with GPS capabilities of success. Failure to conduct proper testing this on the one hand, your device will soon enter the market may end in failure.
GNSS / GPS simulation: general principles of the Global Navigation Satellite System GNSS is a satellite navigation system to provide standard name of global coverage. The term encompasses a GPS, GLONASS, GALILEO, BEIDOU and other regional satellite navigation system.
GNSS appear in the beginning, there are two alternatives can be used to test the navigation system: field testing and laboratory simulation. Today, most of the best practices required test needs to be performed in a controlled, safe laboratory reproducibility conditions. This will not only test normal conditions, can also be tested extremely harsh conditions, including actual and theoretical limits of performance testing. In addition, this approach can also be achieved has yet to push the use or lack of receiver development work complete constellation.
There is real-world test of the real sky a huge drawback because in essence the real sky test has been controlled tests excluded. After summary, compared to the true sky test uses real GNSS constellation, GNSS simulator tests advantages as follows:
1, using the real test of an actual GNSS constellation
2, the signal constellation of uncontrolled
3, the environmental conditions limited control
4, always result in a change in the test conditions can not be repeated
5, suffer accidental FM radar interference and
6, and unwanted signals multipath shutter
7, the error can not perform a test using GNSS constellations
8, field testing and expensive test vehicle
9, subject to available signal constellation GNSS
10, field testing may monitor the competitors
11, laboratory tests using GNSS simulator
12, complete control signal constellation
13, complete control environmental conditions
14, fully reusable
15, no unwanted interference signal
16, non-unwanted signal effects
17, using constellation GNSS error can easily test various types of scene
18, cost-effective testing laboratory in higher
19 can be tested now there and future GNSS signals
20, can safely perform the test in the laboratory
21, perform GPS simulator test
set up and run a test using the receiver simulator is relatively simple. This process can be summarized in two stages:
Definition: definition phase control software using the emulator is required to set test parameters. At this stage, you need to: understand the purpose and operating environment of the receiver under test.
You need to perform confirmatory tests.
Defined with the appropriate test scenarios effect.
Learn how to connect the receiver to the simulator, to maintain the proper RF conditions.
Runtime: at run time phase, the scene will run, and generating an RF signal simulator hardware required. At this stage, you need to:
observe the receiver under test and the necessary control simulator.
Analysis of performance of the receiver. This can be done in real time, you can analyze the recorded data after the test. Access to analog data (data for creating test signals) can be accomplished in various ways, including a data stream, log files, and the like. These data can subsequently be used with a "fact" analog comparison of the data obtained in the performance of the receiver.
GPS function signal generator
May be dependent on the GPS receiver and GPS system provides an effective and efficient means of testing. GPS simulator can be established as a vehicle and satellite motion, signal characteristics, and other atmospheric effects model, a simulation environment, the GPS receiver on the moving platform, so that the receiver can perform navigation in accordance with the actual parameters of the test scenarios. GPS receiver processing an analog signal mode and manner identical to the actual GPS satellite signal.
Compared with the actual GPS signals using a real environment, our GPS simulator can provide an excellent alternative to the test. Real test different sky is performed using the test simulator may be applied entirely to environmental conditions controlled analog and analog satellite signal. Using GPS simulator, the test can easily build and run a variety of different test scenarios, different types of tests implemented, and can completely control the following:
the date, time and location. GPS constellation simulator may generate signal at any location and time. Anywhere in the world or in space scene, as well as past, present and future time, can be tested, and testers all without leaving the laboratory.
The vehicle is moving. Motion simulator can create a model for the carrier includes a GPS receiver, such as aircraft, ships, spacecraft or ground vehicles. It contains vehicle dynamic scenes, covering the world's different from anywhere routes and tracks, can be tested, and the fundamental test of the device without having to physically move.
Environmental conditions. Simulator models the effect affect GPS receiver performance, such as atmospheric conditions, the barrier, multi-path reflections, the antenna characteristics and interference signals. And various combinations of different levels of these effects can also be obtained in the same test in a controlled laboratory environment.
Signal errors and inaccuracies problem. And a simulator control content of the signal characteristics of the GPS constellation. By running the test, the device can determine when various GPS constellation signal errors, how will the performance.
Why use GPS simulator?
When you consider fully operational GNSS system, such as GPS, it's easy to think that only when connected to a suitable test receiver to the antenna, antenna on top of the nearest window, or a vehicle or a building you can check if the positioning receiver can be implemented using the received GNSS signals, tracking and navigation. To some extent, this idea is acceptable. This approach, i.e., is called "true sky" Test herein, indeed substantially verification capabilities of the receiver RF processing circuitry and availability basis.
However, we are interested in testing, and not just to check whether to run. Therefore, the real sky only for simple operation check to make sure the real damage opportunity exists whether to run successfully, but the concept of product planning, design, development, production and integration life cycle, we can not rely on it to perform the test . Using signals in the real world really is the easiest way receiver performance when the real damage or confirm the existence of real operating challenges. The ability to provide additional GNSS simulator is capable of recording and playback system, the complete real-world environment "rich" catch down and replay them in the laboratory.
The reason behind these facts we will do some detailed analysis.
Real sky test problems
must face many unknown factors in the implementation of the real sky test. These unknowns include:
satellite clock error
in the long run, these errors will be corrected in the navigation messages broadcast and amendments, but because such a message update frequency is low, the clock error does exist for some time before the correction.
Advantages simulator: by using satellite simulator, satellite clock error does not exist, unless you want it to exist, and whether it is present or absent, you can accurately understand them and be implemented in a known time.
Track error satellite
navigation message in the nominal position of each satellite in orbit and its physical location is different. This is partly due to the gravitational effects of the sun, moon and Earth's orbit cause errors, thereby forming a perturbation accumulated satellite orbit.
Advantages simulator: the use of simulators, we can eliminate all the wrong track, and use the "perfect" constellation, can be fully quantifiable errors in a controlled manner.
Navigation data errors
as with any data transmission system, error may occur in data modulation, demodulation and transmission. For example, each word in order to improve robustness, GPS navigation system, the last six message parity bit for detecting bit errors. However, errors may still occur, and these errors will not be corrected.
Advantages SYN5203 type GPS signal simulator: there can be no navigation data error occurs when using the simulator, unless it is intentionally applied.
Atmospheric errors
GPS signal must pass through the layers in the atmosphere, but they are mainly composed of two parts, namely the ionosphere and troposphere. Ionosphere (above the earth's surface 70 to 1000 kilometers) of free electrons cause the modulated GPS signal is delayed, and the degree of the delay is proportional to the electron density (the signal passing through the ionosphere propagation velocity will be represented with the ground speed). The same conditions also lead to the occurrence of an equal amount of phase of the RF carrier in advance. (Speed of signal propagation through the ionosphere will be represented with a phase velocity)
Advantage simulator: the use of the simulator, we can disable the atmosphere, to eliminate these errors. On the contrary, we can also be applied to these errors on a known model, and for its overall record.
Multipath
GPS signals belonging to the line of sight signal can be considered as analogous to a beam of light. If the signal beam angle less than the critical angle of reflection falls on the reflecting surface RF, reflection occurs, and a certain attenuation. Thus, the receiver may not only receives the signal beam direct line of sight, and may also receive a reflected version. Receiver impossible to know which of them is truly a sight signals, so both will be utilized, and inherit the reflected signal delay errors exhibited.
Advantages simulator: when using the simulator, we can completely eliminate multipath, you can use a variety of multi-path model is applied to the multi-path signal. With this known, in a controlled manner, we can apply a multi-path, so the effect on the performance of the receiver to obtain accurate analysis and appropriate design modifications or multipath reduction measures. And in the real sky conditions, we simply can not be quantified multipath conditions at any one time, so it is impossible to analyze and improve the performance of the receiver in dealing with multipath.
Interfere with
the GPS signal arrives at the receiver when the antenna has been very weak, because they want to cross long distances to reach the receiver from the satellite. This makes them easily affected by external sources of interference. These disturbances may be deliberate (i.e., jamming or spoofing), may also be non-intentional. GPS vulnerability in the face of interference has been widely documented, in view of space reasons on this page will not be discussed in depth.
Interference will not only introduce errors in the calculation of the receiver's position, it may also navigate to a complete stop. In a real test in the sky, there is interference problems will be very obvious, and simply can not stop.
Advantages simulator: Fortunately, there is interference in the default does not exist when using the simulator, but if necessary, we can also simulate interference by a controlled and repeatable manner. Spirent GSS7765 other interference simulation system, we can apply the presence of interference sources and different distances between the receiver.
Repeatability
When you perform tests on the GPS receiver and found weaknesses in its design, the normal procedure is to design changes aimed at improving receiver. In order to confirm the effectiveness of improvements, you need to repeat the exact same test. If you are using the real sky, we can not ensure that the test performed back to let the receiver go through the same tests as the initial conditions.
The most obvious difference is that, due to the different time, the receiver will be seen quite different constellation. These factors themselves have decided to test conditions it is impossible to duplicate. Others can not remain the same feature is the performance of the satellite and atmospheric effects.
Therefore, the real sky does not apply to design improvements aimed at testing.
Advantages SYN5203 type GPS signal simulator: simulator using constellation, signal runs each time a scene generated are identical. Scenario starts at the same time the same date, and the positions of the satellites will be the same, and even between different relative phase offset signal is the same. This way, you can be sure of the exact same signals for analog receiver each time you run the test.
Controllability
in any comprehensive test, the test conditions have certainty of precise control is essential. Or precisely adjust the design parameters of the system also requires precise control of the trim slightly embodiment the test conditions.
Advantages simulator: when the sky using real testing methods, we almost nothing can be controlled. In addition to testing the physical location of the antenna, the other conditions are not under our control. You can not let time roll back, disable the atmosphere, adjusting the satellite signal, error data, track - and all of this is just what you need complete control over content.
Accuracy
SYN5203 type GPS signal simulator is a sophisticated test equipment, if properly maintained, its performance will be very precise and fully controllable. Signal fidelity of the simulator is much higher than the true signal from the GPS system, not only can be used to test receiver real "laboratory" performance, but also means that the simulator brings the signal to noise levels far below the thermal noise, it will not bring any noise error to the test.
Advantages simulator: two factors are closely associated with the precision of quality and reliability. Simulator design and construction process of precision engineering, quality management and control of these technical categories of the process, will ensure that the equipment can provide reliable service for many years.
The role of recording and playback system should not be underestimated
in order to make a comprehensive assessment of the performance of the receiver, we need to make an assessment of the source of the damage described above. An emerging technology to perform such a test is recorded RF signal and after playback in the laboratory.
Advantages simulator: simulator can definitely control the test environment, and free to add or delete a single source of damage. Simulation may also be used to evaluate the signal not currently in orbit, or are very expensive or difficult to test the limits of movement of the carrier. Indeed, the composite signal generated by the mathematical model represents the ultimate in control.
Business competitiveness
if there is no reasonable business case, no project can survive. Project management and people responsible for setting the budget must be taken seriously on this issue. The idea is usually wrong, and the complexity involved in highly dynamic applications platform field trials compared simulation approach is only way to save money. For example, it is clear that we can not be transmitted to the receiver aerospace grade orbit purpose is to test whether it is working properly. But less obvious is that the simulation may prove less complex applications have their own more cost-effective. A few months driving test on a simulator to be worth the cost, and in many cases also test simulator is more academic than real significance of the choice of site.
Advantages simulator: a leading European car manufacturers have calculated that the total cost of the implementation of real driving test is 5,000 pounds per day. In addition to technical issues we have already discussed the real test, only the financial aspects of the advantages of simulation is enough to prove the great competitiveness.
GPS simulation method
SYN5203 type GPS signal simulator and the motion of the satellite, the signal characteristics, and other atmospheric effects established as a model vehicle, the GPS receiver to reproduce experienced on a dynamic platform environment, enabling the receiver to the test scenario in accordance with parameters, a navigation in the analog RF signal. But the simulator is not able to fully reproduce the magic Box real world, it is not a limitation, but a major advantage. When RF design engineers need a controlled and quantifiable test signal, they certainly would not choose a random noise generator. Similarly, GPS receivers require testers controllable and repeatable test analog GPS signals, not just select a real signal reproducing apparatus.
Since the GPS satellite signal distant from the ground, firing of reaching the ground has been very weak, plus the GPS signal is difficult to remain unchanged, as signal analysis to study the structural features of the GPS signal is not convenient to directly use the GPS signal from the satellite launch. Gps signal generator and having its controllability, reproducibility and flexibility characteristics, may be a GPS system-level simulation to provide as close to the real environment simulation test, thereby testing the performance of the receiver, developed with to a great convenience. Therefore, the GPS signal simulator for research in all fields of study of satellite navigation and positioning have great significance.
SYN5203 type GPS signal simulator is widely used in basic research and timing-based user equipment, the development, production and all aspects of the testing process may complete the ranging accuracy of the test, the test navigation data, test re-acquisition loss of lock, the positioning accuracy of the test, speed precision test, channel delay testing, conformance testing, bit error rate testing, will greatly enhance the work efficiency.
Also applies to rely on satellite navigation and positioning functions related to product research and development testing, such as bike sharing, car sharing, navigation and positioning equipment, electronic fences and other equipment applications. Can greatly improve efficiency, avoid frequent on-site field testing, greatly improving the speed of product development testing deployment.
gps signal transmitter as a complete application system positioned in the field of time, it is currently implemented in terms of the ground can not meet the test requirements, there are many key technologies to be resolved, many functions need to increase and improve.
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