GPS weak signal tracking system based on I/Q branch correlation integral observation filtering

Abstract

The invention discloses a GPS weak signal tracking system based on I / Q branch correlation integral observation filtering. A receiver is used for receiving a satellite signal which is converted into an intermediate frequency signal through down conversion and transmitted to a frequency mixer. The frequency mixer is also used for receiving local sine and cosine reproduction carrier signals outputted by a local carrier digital-controlled oscillator, and outputting a I-branch output signal and a II-branch output signal to a correlation arithmetic unit. The correlation arithmetic unit also receives a local advanced C / A code, an instant reproduction C / A code and a lagged reproduction C / A code, wherein the local advanced C / A code, the instant reproduction C / A code and the lagged reproduction C / A code are generated by a code generator. Results are outputted to an integral eraser, and six-way relevant integral values are generated and outputted to a Kalman filter. The Kalman filter obtains an estimated carrier phase difference, an estimated carrier frequency difference and an estimated code phase difference, and the estimated carrier phase difference, the estimated carrier frequency difference and the estimated code phase difference are transmitted to the local carrier digital-controlled oscillator and the code generator. The system effectively reduces the noise intensity of the satellite signal, can trace the satellite signal better in a weak-signal environment, and improves the tracing precision.

Description

technical field [0001] The invention belongs to the field of GPS signal tracking, in particular to a GPS weak signal tracking system based on I / Q branch correlation integral observation filtering. Background technique [0002] The signal received by the GPS receiver from the satellite is a spread-spectrum modulated signal, and the navigation message can only be obtained by despreading and demodulating the satellite signal in the acquisition and tracking stages. In the GPS signal tracking phase, the signal channel starts from the rough estimate of the carrier frequency and code phase of the current satellite signal obtained in the acquisition phase, and gradually refines the estimation of these two signal parameters through the tracking loop. Under weak conditions, simply increasing the integration time can no longer meet the tracking requirements, and the bit synchronization method can be used to prevent the loop integration time from crossing the edge of the navigation mess...

AI Technical Summary

Problems solved by technology

The extended Kalman filter (EKF) can eliminate the multipath effect in signal tracking, and the model structure is relatively simple, but it cannot effectively track weak signals

By using the fitting method at the triangular peak point of the signal autocorrelation function characteristics, the discontinuity of the Jacobian equation in the EKF operation process can be avoided, but the tracking error is relatively large

Images