Of Ais Baseband Signal And Dsp Implementation

By the development of modern shipping transportation, a equipment, which can auto response and identify, is especial benefit for ocean shipping security,traffic controlling and maritime environment surveilling. This dissertation, basing on simulation, makes a deep research on simulating signal of GMSK (Gaussian filtered Minimun Frequency Shift Keying) baseband modulation and demodulation in AIS (Automatic Identification System) equipment. The technology related in the following makes the modulation and demodulation of baseband signal into realization by TI DSP, at the same time, provides a key technique to develop AIS system inland.Signal forming and different demodulation of GMSK baseband signal are mainly discussed in the dissertation. Gauss Filter, phase integral, SIN table, matched filter, calculate angle, bit-synchronization,output filter,A/D,D/A and etc of GMSK baseband signal are carefully studied through software emulation in SYSTEMVIEW environment. The modulation and demodulation of GMSK baseband signal are carried out by the way of using TMS320VC549 of TI to integrate software and hardware. The system which combine with FPGA , has many characters of flexible structure,more versatility,being liable to maintain and upgrade. Such diathesis made it suitable for blocking design and real time signal processing.Among lots of AIS software protocols, the course of how message 1 in ITU-1371 produce,packed and code is particularly investigated in this article . The output of HDLC data package was coded by NRZI, then conducts the modulation of GMSK baseband signal through DSP. The message was correctly analyzed by SABB receiver, which proved the interconnection and intercommunication between apparatus.A way of using one FLASH to boot four DSP was discussed in BOOT of the system. According to the mode having been setted, the master DSP load program through external parallel interface. Controlled by host DSP, The slave DSP loads the program through HPI. The electro circuit of this mode is comparatively simple, and can cut the cost, but have some complexity to carrying out.After the system has manyfactured, a necessary tested was performed on the baseband board. The quality of signal is well enough to communicate with other AIS equipment and also pass the acceptance check.