Research On Simulation And Analysis Of GPS L2C Singnal

One of the major measure in new GPS modernization initiative announced by the U.S. government is the addition of two civil signals, one of which is denoted as L2C in order to meet the growing requirement of civilian users for high-precision positioning in complex environment. Currently, L2C is transmitted by eight modernized GPS IIR-M satellites. It's expected that it will be fully available in future years. The International GPS Service agency has built up the L2C tracking station network. Because of FEC (forward error correction) and TDM (time division multiplex), L2C lowers the data demodulation and carrier tracking threshold, and makes it possible to track the weak signals in wooded areas and inside buildings. Besides, L2C will provide civilian users the ability to correct for ionosphere delays by making dual-frequency measurements, thereby significantly increasing accuracy. Also with the tight data structure and the separated data and data-less channel, L2C is likely to become the signal of choice for extensive use.This paper addresses the new civilian GPS signal simulation and processing problem and aims at the GPS L2C signal. The signal simulator is one of the most important research methods and tools is, so this paper focuses on the research of GPS L2C signal's software simulation and the acquisition method of the L2C signal, including the circular convolution algorithm based on FFT/ IFFT and the Modified Double Block Zero Padding method. The primary work of this paper can be generalized as the following:1. This paper analyses the GPS L2C signal structure and characteristics, with emphasis on the time-division-multiple-access mechanism and the forward error correction technology, which are different from the C/A Code. Then we do the simulation of CM code, CL code and ultimately the L2C signal through the module design in the Simulink platform. The autocorrelation and spectral characteristics have proved the correctness of the simulation signals, which serves as a theoretical and technical basis for further studying of GPS L2C signal.2. Two acquisition methods are introduced, including the theory reasoning and necessary module design. We realize the two methods by signal simulation experiments, one is the circular convolution method based on FFT/IFFT, the other is the Modified Double Block Zero Padding method. Acquisition results show that the two methods have a stable and superior performance capture..3. Based on the exploration of the navigation, this thesis compares the traditional navigation message and the navigation message structure of civil signals from the perspectives of message structure, message content and message broadcast way, which shows the advancement of the civil navigation message.Based on the analysis of the L2C signals constitute and its generation mechanism, this paper uses the MATLAB to simulate the signal and analyzes the time and frequency domain feature of the simulated signals. The design thought is clear and the feasibility has been proved by simulations, which can be used as the signal resource of the modern GPS receiver. This thesis deeply investigates L2C acquisition methods, one is the FFT-Based Circular Correlation and the other is the Modified Double Block Zero Padding. Finally, this thesis compares the CNAV and NAV. This paper provides a useful exploration and a good reference for the deeper studying of GPS L2C Signal.