| Global Positioning System (GPS) can provide accurate position, velocity and time information to unlimited number users of land, sea, air and space anywhere anytime and all-wheather.With the modernization of the system have been completed and the new system's construction boom, as represented by GPS satellite navigation technology, products, applications and services are in the fast developing.The satellite navigation and positioning receiver is very important and in great demand. In order to carry out the satellite navigation receiver design and research more effectively, this paper, analyzes the the key technologies and implementations of the GPS digital IF signal source in detail.Our Lab had done so much work in the development of GPS receivers, and accumulated a wealth of experience in this process. In this article, the selected carrier frequency and spreading code of the GPS IF signal is 4.309MHz and C/A code with code rate of 1.023MHz, and the carrier modulation is BPSK modulation. Main work in this article includes:Firstly, overall planning for GPS IF signal source program, determining to use FPGA+ DSP architecture hardware platform with serial communication with PC, and DSP, FPGA perform different functions. On this basis, complete the hardware circuit design and PCB layout and design.Secondly, plan and design the relevant function modules within the FPGA, including the carrier generator module, the spreading code generator module and the navigation data buffer module. First analysis, and then select the appropriate parameters and designThirdly, after the planning of functions within the FPGA, to achieve them then doing simulation, verified the correctness and reasonableness of the design by viewing the simulation waveform.Finally, Downloading the program to the user hardware platform, using spectrum analyzer to do the testing and verification of the GPS digital IF signal. |
