Research Of FTSK System In HF Channel Based On FPGA

Short-wave communication has always been an important mean in medium and remote range communications in the world which is widely used in every field. Acquiring simple device, flexible, low-cost, long transmission distance and survivability performance, all the characteristics of short-wave communication contribute to its important position whether for civilian or military use. FTSK is a good way of modulation, combining coding and modulation techniques. As a branch in frequency diversity, it is suitable for the utilization in variable parameter channel, and can reduce the impact of ISI as well as improving system performance effectively, making it an effective technology in overcoming fading and multi-path delay. FPGA, with its powerful function, short development cycle, the capability of being modified repeatedly and improved through software upgrading, has become the most preferred way of hardware designing in the field of wireless communications.The author adopts the idea of software radio, the designing and researching in the short-wave channel FTSK technology are conducted based on the FPGA. Focusing on the frequency range characteristics of short-wave communication, this paper adopts the radio frequency full bandwidth low-pass sampling software radio architecture, and focuses on the FTSK base-band modulation encoding and decoding system.The author at first discusses reflective properties of the ionosphere in short-wave channel and diversity techniques, diversity reception technology can eliminate the occurrence of fading and multipath in short-wave channel, and describes the basic principles, guidelines and error checking and correcting, encoding scheme capacity of FTSK, and then analyzes the bit error rate performance and Matlab simulation is conducted. The second section describes the principles of the major modules of FTSK in transceiver system, including DDS technology, distributed arithmetic FIR digital filters, time slot synchronization and multicode synchronization. Then in Xilinx's integrated development environment ISE9.2i, the author uses Verilog HDL language in programming, combined with Matlab and Modelsim produced by Mentor, the simulation of base transceiver with 4FTSK system is conducted to verify the correctness of the system. Finally, simulation program is downloaded to a FPGA (XC2VP30) chip-based development board of the Virtex-ⅡPro series, with the combination of DAC AD558 chip, and by using the oscilloscope, the correctness of the system hardware is verified.Based on the ideas of software radio, the author applies the FTSK communication system which is designed based on FPGA to short-wave communication, and currently, the FTSK modulation is used in many fields such as underwater communications, this paper may be used as a reference for other applications of the system.