Digital Frequency Synthesizer Research And Design

In this paper, frequency synthesizer technology to the development process are described, the digital frequency synthesis technology and the principle of raising performance of DDS Research. Using DDS devices ML2035 design for a low-frequency sinusoidal signal generator circuit precision, and DDS dedicated device AD9851 combine MCU technology for the Applied Research.This paper focus on the use of FPGA chip and D / A converters, direct digital frequency synthesis, design to achieve a frequency, phase adjustable sinusoidal signal generator system module. The main modules of the system design by 32 four pipeline phase accumulator (ADD), phase modulator (ADD1), seeking fill-quadrant (REG1), the ROM look-up table (LPM_ROM), the symbol for meeting with (REG2), and other parts composition. FPGA development software through the Max + Plus II, will design procedures after the DDS compiler integrated signal source design documents, online programming to FPGA development board, using TEK oscilloscope acquisition output signal. Figure 4.9 is designed to capture the output of the signal waveform. Map output signal frequency, very close to the software simulation results. The system design simulation and test circuit, the output waveform to the technical requirements.DDS is a digital synthesizer, a given clock frequency, the output signal frequency depends on the frequency control characters, the median frequency resolution depends on the accumulator, phase resolution depends on the address line ROM median rate of noise depends on the ROM data bit word length and the D / A converters median. AT89C51 achieve user needs word frequency, waveform generation and communication with the PC, such as logic control functions.Along with the rapid development of microelectronics technology, Direct Digital Synthesis (DDS) has made rapid development, its relative bandwidth, frequency converters, phase continuity, orthogonal output, resolution and integration of a series of performance indicators, etc. far exceeds the traditional frequency synthesizer technology. Using high-performance FPGA design conform to the needs of DDS circuit is a good solution.