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Time synchronization and carrier frequency control of CAPS navigation signals generated on the ground 总被引:2,自引:2,他引:0
The Chinese Area Positioning System (CAPS) works without atomic clocks on the satellite, and the CAPS navigation signals transmitted
on the ground may achieve the same effect as that with high-performance atomic clocks on the satellite. The primary means
of achieving that effect is through the time synchronization and carrier frequency control of the CAPS navigation signals
generated on the ground. In this paper the synchronization requirements of different time signals are analyzed by the formation
of navigation signals, and the theories and methods of the time synchronization of the CAPS navigation signals generated on
the ground are also introduced. According to the conditions of the high-precision satellite velocity-measurement signal source,
the carrier frequency and its chains of the navigation signals are constructed. CAPS velocity measurement is realized by the
expected deviation of real time control to the carrier frequency, and the precision degree of this method is also analyzed.
The experimental results show that the time synchronization precision of CAPS generating signals is about 0.3 ns and the precision
of the velocity measurement signal source is about 4 cm/s. This proves that the theories and methods of the generating time
synchronization and carrier frequency control are workable.
Supported by the Major Knowledge Innovation Programs of the Chinese Academy of Sciences (Grant No. KGCX1-21), the National
High Technology Research and Development Program of China (Grant Nos. 2004AA105030 and 2006AA12Z314), the National Natural
Science Foundation of China (Grant No. 10453001), and the Major State Basic Research Development Program of China (Grant No.
2007CB815502) 相似文献
2.
Wheel-off-loadings and orbital maneuvers of the GEO satellite result in additional accelerations to the satellite itself.
Complex and difficult to model, these time varying accelerations are an important error source of precise orbit determination
(POD). In most POD practices, only non-maneuver orbital arcs are treated. However, for some applications such as satellite
navigation RDSS services, uninterrupted orbital ephemeris is demanded, requiring the development of POD strategies to be processed
both during and after an orbital maneuver. We in this paper study the POD for a maneuvered GEO satellite, using high precision
and high sampling rate ranging data obtained with Chinese Area Positioning System (CAPS). The strategy of long arc POD including
maneuver arcs is studied by using telemetry data to model the maneuver thrust process. Combining the thrust and other orbital
perturbations, a long arc of 6 days’ CAPS ranging data is analyzed. If the telemetry data are not available or contain significant
errors, attempts are made to estimate thrusting parameters using CAPS ranging data in the POD as an alternative to properly
account for the maneuver. Two strategies achieve reasonably good data fitting level in the tested arc with the maximal position
difference being about 20 m.
Supported by the National Natural Science Foundation of China (Grant No. 10703011) and the Science & Technology Commission
of Shanghai Municipality of China (Grant No. 06DZ22101) 相似文献
3.
The solutions of navigation observation equations for CAPS 总被引:2,自引:2,他引:0
Chinese scientists invent the navigation and positioning system based on commercial communications satellites and develop
them successfully into China Area Positioning System (CAPS). In principle, this system is different from the GPS broadcasting
satellite navigation class, where the propagation epoch of original navigation signals for pseudo-range measurement is from
a ground master control station rather than from satellite transponders. This paper addresses the establishment of the three
observation equation models for the navigation and positioning system based on communications satellites, and expresses them
identically to operator equations and optimized models. Furthermore, both algorithms of the linear solution for the observable
characteristic equation and the least-squares solution for the condition number more than 4 are discussed, with several methods
for the exact solution, such as improving the behavior of coefficient matrices, right estimation for the weighted right hand
side and selection of iteration forms of solutions, and the influence of the condition number on improving navigation and
positioning accuracy is also analyzed carefully. Hopefully, all the works would be contributive to further development of
the navigation and positioning system based on communications satellites, and be potentially valuable to other satellite navigation
and positioning systems.
Supported by the National Basic Research and Development Program of China (Grant No. 2007CB815500) 相似文献
4.
Selection of satellite constellation framework of CAPS 总被引:5,自引:5,他引:0
Based on the idea of transmitting the satellite navigation and positioning system, taking the distribution and variation of
the Position Dilution of Precision factor (PDOP), which is closely related with the precision of navigation and positioning,
within the China area as the primary criterion, we analyze and discuss the tentative plan of constellation configuration consisting
of geosynchronous orbit (GEO) communication satellites and inclined geosynchronous orbit (IGSO) satellites for the transmitting
Chinese Area Positioning System (CAPS). We emphatically consider the effect on the PDOP by the three major orbit parameters
including the inclination, eccentricity and right ascension of the ascending node (RAAN) of IGSO satellites, to research the
strategies of the constellation configuration of CAPS through software emulation. Various constellation configurations are
analyzed and compared and the results show that the constellation configuration, consisting of three IGSO communication satellites
in three orbits with the same inclination as 50°, the difference in RAAN as 120° and the same “8” shaped ground track centered
near 115°E and four or five GEO communication satellites within 60°E to 150°E, can satisfy the requirement that Chinese domain
is availably covered and the navigation and positioning with high precision could be obtained. Three relatively excellent
constellation configurations are initially suggested and some concerned issues are discussed in this work.
Supported by the National Basic Research and Development Program of China (Grant No. 2007CB815501) and the Chinese National
Programs for High Technology Research and Development (Grant No. 2007AA12z343) 相似文献
5.
Design and implementation of the CAPS receiver 总被引:2,自引:2,他引:0
In this paper, based on analyses of the Chinese Area Positioning System (CAPS) satellite (GEO satellite) resources and signal
properties, the signal power at the port of the receiver antenna is estimated, and the implementation projects are presented
for a switching band C to band L CAPS C/A code receiver integrated with GPS receiver suite and for a CAPS dual frequency P
code receiver. A microstrip receiving antenna is designed with high sensitivity and wide beam orientation, the RF front end
of the C/A code and P code receivers, and a processor is designed for the navigation baseband. A single frequency CAPS C/A
code receiver and a CAPS dual frequency P code receiver are built at the same time. A software process flow is provided, and
research on relatively key techniques is also conducted, such as signal searching, code loop and carrier loop algorithms,
a height assistant algorithm, a dual frequency difference speed measurement technique, a speed measurement technique using
a single frequency source with frequency assistance, and a CAPS time correcting algorithm, according to the design frame of
the receiver hardware. Research results show that the static plane positioning accuracy of the CAPS C/A code receiver is 20.5–24.6
m, height accuracy is 1.2–12.8 m, speed measurement accuracy is 0.13–0.3 m/s, dynamic plane positioning accuracy is 24.4 m,
height accuracy is 3.0 m, and speed measurement accuracy is 0.24 m/s. In the case of C/A code, the timing accuracy is 200
ns, and it is also shown that the positioning accuracy of the CAPS precise code receiver (1 σ) is 5 m from south to north,
and 0.8 m from east to west. Finally, research on positioning accuracy is also conducted.
Supported by the Knowledge Innovation Program of Major Projects, Chinese Academy of Sciences (Grant No. KGCX1-21) and the
National High Technology Research and Development Program of China (Grant No. 2004AA105030) 相似文献
6.
The Chinese Area Positioning System (CAPS) is based on communication satellites with integrated capability, which is different
from the Global Positioning System (GPS), the International Maritime Satellite Organization (Inmarsat) and so on. CAPS works
at C-band, and its navigation information is not directly generated from the satellite, but from the master control station
on the ground and transmitted to users via the satellite. The slightly inclined geostationary-satellite orbit (SIGSO) satellites
are adopted in CAPS. All of these increase the difficulty in the design of the system and terminals. In this paper, the authors
study the CAPS configuration parameters of the navigation master control station, information transmission capability, and
the selection of the antenna aperture of the communication center station, as well as the impact of satellite parameters on
the whole communication system from the perspective of the transmission link budget. The conclusion of availability of the
CAPS navigation system is achieved. The results show that the CAPS inbound communication system forms a new low-data-rate
satellite communication system, which can accommodate mass communication terminals with the transmission rate of no more than
1 kbps for every terminal. The communication center station should be configured with a large-aperture antenna (about 10–15
m); spread spectrum communication technology should be used with the spreading gain as high as about 40 dB; reduction of the
satellite transponder gain attenuation is beneficial to improving the signal-to-noise ratio of the system, with the attenuation
value of 0 or 2 dB as the best choice. The fact that the CAPS navigation system has been checked and accepted by the experts
and the operation is stable till now clarifies the rationality of the analysis results. The fact that a variety of experiments
and applications of the satellite communication system designed according to the findings in this paper have been successfully
carried out confirms the correctness of the study results.
Supported by the National Basic Research and Development Program of China (Grant No. 2007CB815504) and the Technology Research
and Development Program of China (Grant No. 2007AA12z343) 相似文献
7.
GuoXiang Ai PeiXuan Sheng JinLin Du YongGuang Zheng XianDe Cai HaiTao Wu YongHui Hu Yu Hua XiaoHui Li 《中国科学G辑(英文版)》2009,52(3):376-383
This work describes the barometric altimetry as virtual constellation applied to the Chinese Area Positioning System (CAPS),
which uses the transponders of communication satellites to transfer navigation messages to users. Barometric altimetry depends
on the relationship of air pressure varying with altitude in the Earth’s atmosphere. Once the air pressure at a location is
measured the site altitude can be found. This method is able to enhance and improve the availability of three-dimensional
positioning. The difficulty is that the relation between barometric pressure and altitude is variable in different areas and
under various weather conditions. Hence, in order to obtain higher accuracy, we need to acquire the real-time air pressure
corresponding to an altimetric region’s reference height. On the other hand, the altimetry method will be applied to satellite
navigation system, but the greatest difficulty lies in how to get the real-time air pressure value at the reference height
in the broad areas overlaid by satellite navigation. We propose an innovational method to solve this problem. It is to collect
the real-time air pressures and temperatures of the 1860 known-altitude weather observatories over China and around via satellite
communication and to carry out time extrapolation forecast uniformly. To reduce data quantity, we first partition the data
and encode them and then broadcast these information via navigation message to CAPS users’ receivers. Upon the interpolations
being done in receivers, the reference air pressure and temperature at the receiver’s nearby place is derived. Lastly, combing
with the receiver-observed real air pressure and temperature, the site’s altitude can be determined. The work is presented
in the following aspects: the calculation principle, formulae, data collection, encoding, prediction, interpolation method,
navigation message transmission together with errors causes and analyses. The advantages and shortcomings of the technique
are discussed at the end.
Supported by the National Basic Research Program of China (Grant No. 2007CB815500), the National High Technology Research
and Development Program (Grant No. 2004AA105030), the Pilot Project of the Knowledge Innovation Program of the Chinese Academy
of Sciences (Grant No. KGCX1-21), and the National Natural Science Foundation of China (Grant No. 10453001) 相似文献
8.
A new method of ionospheric-free hybrid differential positioning based on a double-antenna CAPS receiver 总被引:1,自引:1,他引:0
Chinese Area Positioning System (CAPS) is a transmitted satellite navigation system moved by the Chinese Academy of Sciences.
Three basic modes of navigation and positioning with CAPS are given, and then a comparative analysis is made in this paper.
In terms of the principle that the ionospheric delay is at an inverse ratio to the frequency square, a new ionospheric-free
positioning method based on a double-antenna CAPS receiver is put forward. Then the hybrid differential observations and the
solving equations and algorithms for one epoch and multi epochs are deduced according to the basic principle of the method.
The method may remove the global errors in signal emission, propagation, transmission and receiving (e.g., ionospheric delay,
hardware delay, and clock error). So it is very convenient for the single-epoch solution and multi-epoch navigation and positioning,
and may efficiently improve the precision of real time CAPS navigation. Furthermore, the method can be used not only for the
geometric orbit determination of CAPS GEO and IGSO satellites and the navigation and positioning, but also for the estimation
of the tropospheric zenith delay, which is useful for the study of water vapor changes in the atmosphere. Polynomials are
used in this method to express the tropospheric zenith delay and CAPS satellite orbits within the limited time interval, which
reduces the number of unknown parameters and thus speeds the computation.
Supported by the Knowledge Innovation Project of the Chinese Academy of Sciences (Grant No. KGCX1-21), the National Basic
Research Program of China (Grant No. 2007CB815500), the National High Technology Research and Development Program of China
(Grant No. 2006AA12z303), the National Natural Science Foundation of China (Grant No. 40774009), and the Special Project of
Taishan Scholars of Shandong Province of China (Grant No. TSXZ0502) 相似文献
9.
This paper briefly introduces the maneuverable feature of the slightly inclined geosynchronous orbit (SIGSO) satellites under
a new control model degraded from the geosynchronous orbit (GEO) communication satellites which will retire as most of the
fuel in these satellites has been consumed. Basing on the transmitting Chinese Area Positioning System (CAPS), the authors,
by analyses, indicate that such satellites can make an improvement to CAPS constellation configuration, especially to the
PDOP value from simulation. The results show that the use of SIGSO satellites can (1) actualize three-dimensional (3D) navigation
and positioning compared with the situation, which, only using GEO satellites, cannot be carried out, and improve navigation
and positioning accuracy to some extent; (2) reuse the communication services of these satellites for more years, and GEO
communication satellites will be retired at a later time and delay their time to become space debris and reduce their pollution
of the space environment, so that valuable space resources are maximally used. As for the use of these satellites in the transmitting
positioning system, the authors present some views and suggestions in this work.
Supported by the National Basic Research and Development Program of China (Grant No. 2007CB815501) and the Chinese National
Programs for High Technology Research and Development (Grant No. 2007AA12z343) 相似文献
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