Design, Implementation And Application Of Gmsk High-speed Data Transmission Machine

With the rapid development of VLSI, digital receiver and software defined radio (SDR) have become a popular research area in modern communication systems. Nowadays, baseband, intermediate frequency (IF) and even radio frequency (RF) analog signals can be converted to digital signals in digital receivers. And the subsequent digital demodulation is prone to be achieved on a programmable and versatile hardware platform by the software using digital signal processing technology.In this dissertation, the design and FPGA implementation of a high speed GMSK modem in wireless video transmission system are studied. And the main contents are presented as follows:(1) The basic concepts and development trends of digital receiver and software defined radio are briefly introduced.(2) Digital communication theories such as sampling theorem, multirate signal processing theory, optimum receiver and bit synchronization are demonstrated.(3) The design of a 5Mbps GMSK baseband modem is discussed, and the FPGA implementation of early-late gate bit synchronization algorithm is investigated. A polyphase filter-based architecture for the efficient implementation of baseband digital receiver is finally derived.(4) The application of LMS adaptive equalizer in GMSK baseband receiver is studied.(5) The choice and usage of FPGA, A/D (Analog to Digital Converter), D/A (Digital to Analog Converter) and amplifiers in the GMSK baseband modem are explained, and the system hardware structure is figured out.(6) The development procedure of FPGA in the GMSK baseband modem is introduced.(7) The test scheme and results of GMSK baseband modem and FM modem are presented. And finally, outdoor experimental results of the wireless vedio transmission system are given.The high speed GMSK modem has already achieved 15km wireless transmission of 5Mbps MPEG-2 video data stream in outdoor experiment. And it is of great value in practical use.