The Key Technique Research Of Low Power IMU-aided GNSS Receiver

With information projects like ‘Intelligent City’ advancing, positiontechnologies such as GNSS have more impact on human’s life and work.In civil areas, GNSS positioning technology under bad signal environmenthas been hot area in research. GNSS positioning technology faces twomain challenges: low-quality signal and power limit, especially forhand-held devices. In this thesis, high sensitivity GNSS receiver designwith low-power techniques is being researched. The main content of thisthesis is baseband signal processing, including acquisition (bitsynchronization is included), tracking with an IMU, which helps trackingloop work in intermittent mode.Firstly, coherent and non-coherent accumulation is used to improveacquisition sensitivity, and an alternate half-bit integration scheme helpsdealing with bit transition problem. Simulation shows that acquisitionsensitivity reaches23dBHz when signal dynamic is lower than50Hz/s.Furthermore, to reduce computation complexity and increase acquisitionspeed, mixed-code search is adopted, and simulation shows that whenC/N0is high, it would have3dB enhancement. Finally, an frequencycompensated bit synchronization method is compared with histogrammethod, and simulation shows it would have7-8dB improvement with thesame signal processing length.Secondly,2nd order FLL aided3rd order PLL with a DFT frequencydiscriminator is adopted to track signal. Simulation shows that sensitivitywould increase2dB compared to Arctan frequency discriminator andtracking sensitivity reaches14dBHz when signal dynamic is less than5Hz/s, and200ms integration is used. Furthermore, tracking loop works inintermittent mode, and an IMU helps to switch between different states. This thesis put an emphasis on how to re-track signal quickly whentracking loop switch back to tracking state. Analysis shows thatintermittent tracking would reduce80%power in best situation.Finally, the algorithms and techniques researched above work for bothGPS L1signal and the newly released BDS B1I signal (2012Dec.). In sum,the design, analysis and simulation in this thesis serve as guidelines whendesigning practical and commercial GNSS solutions.