GPS L2C signal tracking method

Abstract

The invention provides a GPS L2C signal tracking method. The unscented Kalman filter based method involves: adopting a CM code and a CL code for simultaneous tracking so as to reduce a carrier wave and code tracking threshold so that energy waste and precision loss are avoided, and arranging a weight coefficient and enabling the coefficient to be superior to any an individual CM or CL code tracking mode. The unscented Kalman filter can reduce the complexity of tracking calculating and has higher tracking sensitivity and precision. By using the method provided by the invention, not only can the tracking success rate of an L2C signal in a low signal-to-noise ratio environment be improved, the calculating complexity is also reduced, the calculating speed is faster, thus conditions are created for the application of a GPS L2C signal in a weak-signal condition, the potential economic and social values are high, and the method also takes important significance in the positioning application field of a GPS receiver in the low signal-to-noise ratio environment.

Description

technical field [0001] The invention belongs to the technical field of wireless communication, and in particular relates to a GPS L2C signal tracking method. Background technique [0002] At present, GPS (Global Positioning System, Global Positioning System) provides global users with a new civil signal L2C signal, which uses a special civil medium length code (CM code) and civil long code (CL code) for time division multiplexing , more suitable for weak environments such as indoors, tree-lined roads, and tunnels. [0003] GPS L2C signal navigation data is only modulated on the CM code, no navigation data is modulated on the CL code, and the CL code channel only exists as a pilot channel. For the time-division multiplexed GPS L2C signal, the traditional tracking method is to generate two zero-padded local codes of CM and CL locally, and then use two independent tracking loops, one to track the CM code and the other to track the CL code. Since the CM code and the CL code on...

AI Technical Summary

Problems solved by technology

Since the CM code and the CL code only occupy half of the time of the entire signal, compared with the C / A code in terms of tracking accuracy, whether only the zero-padded local CM code or the zero-padded local CL code is used to track the L2C signal , will result in a 3dB loss of accuracy, because the signal energy used only accounts for half of the total energy, and the energy of the other channel is ignored, resulting in a waste of signal energy

[0004] At the same time, the low signal-to-noise ratio, high dynamic and complex and changeable environment also endows the GPS signal with strong nonlinear characteristics, making the measurement equation nonlinear, while the traditional extended Kalman filter (EKF) tracking loop structure must be linearized To achieve this, at the triangular peak point of the signal autocorrelation function characteristics, only the fitting method is used to compensate for the nonlinearity of the Jacobik equation, resulting in tracking errors

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