| Global navigation satellite system (GNSS) is a space based wireless positioning system.After GPS of America and GLONASS of Russia, EU has planed to build Galileo navigation satellite system since 2003. China has also prepared to build"BeiDouâ…¡"global navigation satellite system based on the succeed of"BeiDouâ… "double satellites positioning system. For these positioning systems using wireless signal, the attenuation of signal is an unavoidable obstruction. Such as GPS and GlONASS, the orbits of satellites are generally 20000 kilometers high. When the signal arrived at the ground, it will be attenuated greatly. From this reason, the navigation signals is easy to be obstructed by the buildings, tree, wall and so on. In some situations, such as urban canyons, positioning in valleys and in deep open-cut mines, the navigation signals usually are not able to be received, this will bound the application of satellite navigation technique more or less. Moreover, because of the mask angle of the receiver, navigation satellites are usually located at the up sky of the antenna. This will result to GPS positioning accuray of height component is generally 2 or 3 times worse than the horizontal component. As a result, in some situation, such as airplane landing, dyke deformation monitoring, some kinds of augmenting techniques should be needed.Pseudolite positioning technique is an exciting technology whose potential can resolve the problems above. Pseudolites can increase the number of satellites and improve the geometric strength of positioning solutions. The overseas research on pseudolite can be backward to 1970, but the domestic research is just beginning.This dissertation is supported by a grant from Science and Technology Commission of Shanghai Municipality (Project No.05dz15006), The purpose of this dissertation is to explore the theoretical analysis and application research on the core technique, Pseudolite technique. Firstly a practical pseudolite transmitter has been designed. Then the integration model of GPS and pseudolites is presented to impove the positioning accuracy. Finally a corresponding experiment has been carried out.The emphasis in this work has been placed on1. The signal structure of pseudolites has been researched to compare the difference between pseudolite and GPS, which is a precondition to design the hardware of pseudolite. The generation and structure of C/A code and D code are also introduced in this dissertation, moreover the transmitting power of the pseudolite. The results will do great means to the pseudolite design of medium-frequency module and RF module.2. A design of practical pseudolite generator has been presented After analyzing the principle and structure of pseudolite signal. The schematic and individual modules are also be proposed, this will succeed to a series of work from baseband to the upper frequency conversion. The actual experiment has been carried out using the designed pseudolite. The ephemeris of pseudolite was obtained with software receiver and Matlab. As a result, GPS satellites and pseudolite can both be locked using Off-The-Shelf GPS receivers.3. Geometric DOP has been investigated to compare effects of the additional pseudolite observations. Firstly we estimate the extremum of DOP using matrix theory, and because the calculation of DOP is extremely complicated. This paper has presented an improved coordinate system in order to decrease the amount of variables to calculate the property of DOP. Using matlab, we analyze the DOP changing tendency based on the azimuth and elevation of the satellites.4. Using pseudolite can improve DOP and obtain a high positioning accuracy; on the other hand, we can use DOP to search the optimal location of pseudolites. A suit of visual and analytical software has also been designed using DOP as a criterion. The input of this software is the initial location of pseudolite; as a result, we have an overall search and analysis to electronic map. The result of this software will redound to make an impoved configuration of pseudolites.5. Some key issues in the application of pseudolite, such as near-far effect, pseudolite synchronization and multipath problem were discussed in detail. Using Taylor series expansion, the nonlinear pseudolite models are usually linearized, so the linearity error of pseudolite was presented. Considering the high-level redundancy of Thaler series spreaded, an impoved method is presented to impare the linear error of the pseudolite observation.6. GPS and pseudolite integrated carrier smoothed code difference positioning model has been presented in this dissertation. With the location of pseudolite as a consideration, a suggestion was brought out to improve the classical Hatch filter.The smoothing window width of pseudolite should be analysised in actual experiment. The result has been processed to show that the integrated GPS/PL model can improve the positioning accuracy of stand-alone GPS.
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