The Research And Development Of High Sensitivity GPS/Galileo Dual Mode Navigation Receiver

With the growing demand for Location Based Servers(LBS), particularly the growing demand for application of urban and indoor positioning, the development of high performance receiver——High Sensitivity receiver has become a hot in the navigation field. Meanwhile, Europe Galileo project brings this field a new impetus. Because of the compatible characteristic of Galileo Open Servers(OS) signal and GPS signal, the development of dual mode high sensitivity navigation receiver has become the trend of mass market receivers & chipset. This dual model receiver is completely different from traditional GPS/Glonass combined positioning receivers because of the community RF module and the compatible correlation channel. So the design is more simple, and the accuracy of observation value is improved. Through effective use of the two satellite constellation to improve the usability, the dual mode receivers are suitable for application in urban city.Under the background of EU-China Galileo cooperation program, Shanghai Science and Technology Commission approved the project of high sensitivity dual model navigation receiver. Based on the project demand, this dissertation focuses on some key technologies about it. This study addresses the following elements.In view of the indoor positioning characteristics, a system-level analysis of AGNSS (Assisted Global Navigation Satellite System) is described, especially the assisted time and frequency information. Base on the Mixer-Free Quadrature Demodulation technology, the sampling rate is selected to reduce the algorithm complexity. The frequency shift of local oscillator in A/D sampling is unified with satellite Doppler velocity. As many high sensitivity algorithms are based on FFT, the time parallel and frequency parallel FFT algorithm is analyzed. For AGNSS receivers, the code phase is the sufficiency value for PVT algorithm, so the signal acquisition is the key technology of high sensitivity receiver. Based on the Maximum Likelihood receiver principle,Coherent-Noncoherent integration is analyzed. It has serious square loss Characterization, especially in real data. Differentially coherent integration algorithm which is frequently used in spread spectrum communication is analyzed in detail for high sensitivity signal detection. In view of the cross correlation problem of indoor position, a hypothesis with cross correlation is presented, and the detection performance is compared with the mitigation condition. Analysis of the real GPS data shows that the Differentially coherent has average 0.75dB superior performance than the Coherent-Noncoherent. A carrier to noise estimation algorithm is improved, which is more suitable for high sensitivity condition. In order to design the compatible correlation channel structure, a new modulation of Galileo signal——BOC(Binary Offset Carrier) is analyzed. It has a lot of advantages, but the resource of receiver is multiplied by 10. Because the acquisition of the first satellite is the key process of high sensitivity receiver, a GPS fast acquisition channel structure based on FFT is presented. Due to the complexity of Galileo signal, it is hard to design the fast acquisition channel. Through the use of Galileo modulation, a new fast acquisition algorithm which performs multiplication on Pilot channel and Data channel is analyzed. Compared with single channel acquisition, it improves the sensitivity 2dB, and reduces the number of frequency search bins. Based on this approach, a dual mode fast acquisition and track composite correlation channel structure is presented, and the hardware resource is effectively used.The memory space is the bottleneck of Snapshot position method. Galileo signal doubled the bandwidth, so this problem is more serious. By weighing the relationship between output SNR and storage memory, GPS and Galileo optimum bandwidth is analyzed, and a simple dual mode filtering solution is presented which adopts the minimal sampling rate. For this optimum bandwidth, the position accuracy is theoretically analyzed, and the test results show that it is feasible.If we want to take an ulterior step to improve the sensitivity, phase noise affects the implementation of the long time integration algorithm. Through modeling the phase noise, a phase estimation technology based on Viterbi algorithm is analyzed. Combining this algorithm with full coherent integration which has better sensitivity capability, data analysis shows that it gets average 1.5dB gain, and it achieves some effect in restraining the phase noise. The prototype system of this project is introduced, some scheme and flow of this experimentation is described. Several tests are implemented and some results are validated.Some outcome of this paper had been successfully used in the development of high sensitivity navigation prototype, and the results of initial tests showed that the sensitivity is -156dBmW.