Study On Local Ground-based Navigation Systems Baseband Signal Transmitter On

Land navigation system is a hot research field in recent years, compared with satellite navigation, inertial navigation, it is not affected by the weather and the environment, and the maneuverability is strong. By the establishment of navigation site on the ground, the fire arrow can achieve precision navigation.Combined with the practical experience our laboratory in GPS navigation guidance in the process of research in recent years, and draw lessons from the related technology of GPS navigation. This paper expounds the land navigation system structure and the methods to resolve related difficulty. The main work is as follows:Firstly, introduced the system level structure of land navigation system.Through scattered four or six stations in our positions around to offer navigation signal to realize the projectile’s accurate navigation.Then introduce the time tick methods used by each base station system.Second, determine the rate of navigation data of the base station spread spectrum code、 the code rate and the way of modulation and other technical specifications. The biggest characteristic of this system is the base of the spread spectrum code、code length and code rate and carrier frequency is adjustable. According to certain technical specifications, as well as analysis on every link of the whole navigation system, can roughly estimate the error range of this land navigation system. At the same time, through the analysis of the link budget, the minimum transmission power transmitter can be obtained.Thirdly, according to the requirement of the system, base station signal transmitter selected DSP+FPGA architecture. Realize the spread spectrum code generation, spread spectrum modulation and carrier modulation. In addition, FPGA can be controlled by DSP by sending control words to change the spread spectrum code length, code rate and carrier frequency.Finally, in the hardware platform, accomplish the signal transmitter’s each function module debugging and implementation. Results show that the design of the base station transmitter operating smoothly and have achieved good results.