Design Of Loran-C Signal Generator Based On DDS Technology

A high performance Loran-C signal generator which can generate Loran-C signals include noise and all kind of interference is needed at the process of design digital Loran-C receiver, the capability of Loran-C signal generator by using traditional analog or digital electrocircuit exist many disadvantage such as diffcult to realize, biggish error in resolving capability, hard to adjust and add noise and environment interference. With steady advances and development in modern electronic technology especially very large scale integration technology (VLSI), the capability of signal generator by using Field Programmable Gate Array (FPGA) combined with direct digital synthesizer (DDS) technique will be improved greatly and the difficulty of designing will be reduce|d observably.So based on the research and design previous, firstly design Loran-C signal generator adopt FPGA combined with DDS technique.This paper is focused on the design of Loran-C signal generator based on FPGA combined with DDS technology. Firstly, it introduces the development history of the Loran-C System and DDS technique. Secondly, it introduces the data structure of Loran-C system, and then it introduces the basic theory of direct digital synthesizer technique.Furthermore, this paper introduces the construction of the design which is based on Xilinx Inc high performance FPGA according to the requirement of the signal generator, and the system is implemented based on the DSP and FPGA co-processing. The design chooses Xilinx Inc Virtex-5 family FPGA-XC5VSX50TFF665 as signal generator to generate Loran-C signal and its control logic, and chooses TI Inc TMS320C6713 as central controller to code the time information according to the code structure of Loran-C sent to FPGA used to control the generation of Loran-C datalink signals. For the hardware circuit design of the system, the paper presents the conceptual frame of the signal generator and expands the principle of the signal generator, and expatiates that the main chips used in the signal generator and the main modules of hardware circuit, the designs of the hardware scheme circuit and the PCB of the system board is based on PADS2005, and simulate the signal integrity of the significant signal wires after accomplished the hardware scheme circuit which proves the correctness of the hardware scheme circuit.At last, the Loran-C signal generation module based on DDS is realized according to Loran-C signal generation theory and the debugging results are given.