Design Of Direct Digital Frequency Synthesizer Based On FPGA

Direct Digital Synthesis technology that was put forward is a method of all-digital frequency synthesis at the seventies of the nineteenth, which betake a constant signal source of input reference clock to produce output signal of phase and frequency's adjustable to the way of date processing .After 30 years of development, it has become the main form of frequency synthesize. Because of excellences of high frequency resolution,fast frequency conversion speed,phase continuous,low phase noise and so on, DDS is widely used in field of communication,radar,remote telemetry,navigation,PCS/PCN system. In recent years the rising field programmable gate array (FPGA ) with excellences of high integration,fast speed,high reliability,rich resources and so on, is very suitable for the digital part design of DDS system.The article focuses on the realization of direct digital frequency synthesizer, and study the direct digital frequency synthesize by improving the key part structure of DDS.In this paper, first, we analyze the working principle and structure of direct digital synthesizer , and detailedly analyze various methods of phase transforming scope.Optimizing NCO design of a key part of DDS, and combining the Brent-Kung binary tree structure and carry select adder to realize the phase accumulator, and reduce the delay. Improve traditional Cordic algorithm, using parallel Cordic algorithm make phase transform scope, emphatically introduce the method of rotation direction of Cordic algorithm calculated. Using Verilog hardware design language write programs to various parts of the design, and simulate these programs in QuartusⅡ, verify their reasonableness. Giving the overall performance of the system by simulation, then downloading to FPGA to verify. Finally detailedly analysis output spectrum of direct digital frequency synthesizer, and give a number of ways to reduce the stray.