Band Carrier Frequency Synthesis And Measurement Technology Research

With the development of synchronous broadcasting technology, the synchronous carrier signal generator based on the homologous modulation technology and the frequency synthesis technology is becoming highly valued. Direct Digital frequency Synthesis (DDS) is widely used in frequency synthesis. Based on the theory of the basic principle of DDS, the paper studies the implementation methods of hardware and software of DDS, a carrier signal synthesis system of medium-wave synchronous broadcasting is designed.After extensive research on the implementation and circuit design of DDS technology, the paper puts forward a design which uses ARM7 series microcontroller as the control unit, Field Programmable Gate Array (FPGA) for the frequency measurement unit. The circuit includes DDS module, filter and amplification module, ARM control module, liquid crystal display module, FPGA module and power module. The FPGA module carries out the frequency measurement of the output frequency and the serial communication between ARM and FPGA. The ARM module controls DDS to synthesis frequency for our need. It also handles the LCD module for displaying.The system software is also developed, which contains the DDS control program, the frequency measurement program and the keyboard control program.The DDS control program is used to implement the ARM microcontroller to control four ways of DDS circuit to generate designated frequency. The frequency measurement program using vhdl language includes frequency measurement and dada transmission based on serial communication. After debugging, four ways of frequency synthesis circuit controled by the keyboard could generate designated signal which is synchronous with GPS.The system also includes the capability of filtering and amplification, frequency measurement and displaying.