Design Of Baseband Tracking Loop For Low Power GNSS Receiver

The rise of the Internet of Things(IoT)has brought about an upsurge of research and development of IoT technology and equipment.Accurate,real-time positioning is an important feature of IoT devices.The Global Navigation Satellite System(GNSS)is a most widely used navigation and positioning system.However,the traditional GNSS receiver module has high power consumption and it is difficult to meet the requirements of IoT devices.Therefore,low-power GNSS receivers have become a research hotspot.Global Positioning System(GPS)is the most widely used satellite system in GNSS.The design and evaluation will center on GPS.The GPS positioning module operates intermittently in the architecture of GPS receiver assisted by Inertial Navigation System(INS).When GPS module turnes off,the low-power INS module performs inertial navigation and positioning,so that the system operating power consumption is low.The power consumption of the positioning system mainly depends on the acquisition and tracking process of the GPS module.Therefore,how to design a tracking loop to reduce the system positioning power consumption has become the focus of this study.A fast traction tracking loop based on Kalman filter is designed in this thesis.The tracking loop uses the user position to predict the GPS signal code phase and Doppler,so that once the GPS module turns on,the code phase and Doppler is within the tracking loop pulling range,so that the receiver can directly enter the tracking state to avoid the acquisition process.After the receiver enters the tracking state,there is a large error between the local copy signal and the received GPS signal.In the code tracking loop and carrier tracking loop,the method of frequency offset compensation is used to counter the coherent integration attenuation caused by the frequency difference and improve the accuracy of the code phase detection and frequency discrimination.After obtaining phase and frequency deviation,a Kalman filter is used as a loop filter to first accelerate the loop traction process with a large noise bandwidth,and then gradually reduce the noise bandwidth to obtain a preciser pseudorange and Doppler measurements.The simulation results show that the designed fast traction tracking loop has a pseudorange accuracy of 3.25 m and a Doppler accuracy of 1.65 Hz under the conditions of 40 dB.Hz signal power,100 ms traction time,initial error 30 m pseudorange error and 26 Hz Doppler error.Simulation and evaluation of the receiver based on fast traction tracking loop algorithm is finished by using software receiver.Simulation experiments show that the power consumption of the INS-assisted GPS receiver based on the designed fast traction tracking loop is 3.0mW,the pseudorange accuracy is 4.41 m at-130 dBm,and the positioning accuracy of 5m Circular Error Probable(CEP)can be achieved with a Position Dilution of Precision(PDOP)of 1.25.