Research Of High Sensitivity GPS Positioning And Intregrated Nevigation Technology

Nowadays, Global Positioning System (GPS) is applied broadly in the world, but in the situation, the present receivers are usually in the outdoor environment where there are good GPS signals. Since the environment around us has become more and more complicated, GPS positioning technology will no be able to satisfy people's need. Compared with the common circumstance, as outdoors, GPS signals power will be weaken much, and its reliability and position accuracy will be debased much in the low signal to noise ratio (SNR) environment. However, the the low SNR environment,such as indoor environment, is one of the main environment where humans live, there are a lot of applications needs of GPS,high sensitivity GPS (HS-GPS) positioning technology will be studied to solve the problem. In the application of GPS,HS-GPS positioning technology is a potential application domain of GPS. So researches on HS-GPS indoor position technology are necessary in the extreme to implement high accuracy position in indoor environment and extend application area of GPS, the researches on HS-GPS positioning technology have become hot points currently.HS-GPS positioning technologies in the indoor environment are studied, weak GPS signals acquisition technologies, which is one of the difficulties on HS-GPS positioning technology are studied and analyzed in detail, a weak GPS signals acquisition algorithm based on Duffing oscillators array is proposed, Doppler frequency of GPS signals is acquired. Finally, C/A code phase of GPS signals is acquired using differentially coherent acquisition algorithm.In addition, an integrated navigation technology of improving vertical positioning accuracy based on GPS/barometric altimeter is studied. Two integrated navigation algorithms based on adaptive federated Kalman filtering and particle filtering are proposed. The integrated navigation system is efficient in improving vertical positioning accuracy, reliability, adaptivity and real-time processing rate, ensures an airplane fly precisely over an assigned, and endow it with the ability of precision approach and landing in complicated weather condition.The main work and innovations accomplished in this dissertation are as follows: (1)GPS positioning technology, integrated navigation technology and key points of HS-GPS positioning are discussed. In addition, characteristic of GPS signals is analysed in indoor and airdrome environment, GPS signals acquisition technologies are studied in low SNR environment.(2) A lot of weak GPS signals acquisition algorithms are studied, such as coherent integration,non-coherent integration,circular correlation with multiple databits and circle correlation. Discuss disadvantage of current GPS signals acquisition algorithm and propose improvement methods, finally detection performance of current detection algorithm is discussed using simulation results.(3)Weak signals detection technologies based on chaotic oscillator are studied, several chaotic oscillators are discussed. Model, dynamics characteristic and estimation method of Duffing oscillator are studied. Two models of Duffing oscillator are simulated. Phase charts of Duffing oscillator with different state are studied. Dynamics characteristic of Duffing oscillator are known by means of phase chart.(4) A weak GPS signals acquisition algorithm is proposed based on Duffing oscillator array by means of weak signals detection theoretics based on chaotic oscillator. Lyapunov exponent is adopted to aid the judgment on the state of chaos oscillator system, and numeric iteration procedure is used to calculate the exponent. Firstlly, decide whether weak GPS signals exist or not by means of Lyapunov Exponents algorithm. Carrier's Doppler frequency of GPS signals is obtained if GPS signals exist by means of Lyapunov Exponents calculation. At last, C/A code phase is obtained in virtue of above carrier's Doppler frequency by differentially coherent integration technique. This detection method breakes through traditional two dimension search process.In the process of weak GPS signals acquisition, carrier's Doppler frequency and C/A code phase of GPS signals are acquired solely.This acquisition algorithm can acquire GPS signals at extreme low power, and improve detection sensitivity level of GPS receiver.(5) Weak GPS signals acquisition technologies based on differentially coherent integration are studied, GPS signals acquisition algorithm based on differentially coherent integration is proposed when carrier's Doppler frequency of GPS signals is known. Detection probability, false probability and detection threshold are studied.SNR loss introduced by differentially coherent integration detection algorithm is analysed.Improvement effects on detection sensitivity are analyzed quantitatively. Traditional acquisition algorithm is compared with differentially coherent integration detection algorithm, by implementing rigorous mathematical analysis and simulating, the results prove the advantage of detecting weak GPS signal.(6) Integrated navigation system based on GPS/barometer is studied.A scheme of integrated navigation system of improving vertical positioning accuracy based on GPS/barometric altimeter is analyzed.Two data fusion algorithms based on adaptive federated Kalman filtering and particle filtering are proposed. Vertical positioning accuracy of the fusion algorithm is analyzed.Simulation results prove that the integrated navigation can improve vertical navigation accuracy of airplane.(7) Finally, several conclusions of the dissertation are drawn and the research subjects in the future are proposed.