The Research Of Signal Generation Technology Based On DDS

The direct digital synthesis (DDS) technology is superior to the conventional frequency synthesis in the frequency resolution, frequency switching time, phase continuity and integration. It is widely used in the fields of radar, communications, space electronics and instrumentation. The paper analyses the DDS technology and completes the design of arbitrary signal generator by FPGA.This paper describes the structure and working principle of DDS in detail and analyses the spectral characteristics of DDS in ideal and non-ideal cases. It summarizes the impact factors of the output signal quality and studies the phase truncation error, amplitude quantization error and D/A conversion error. Then it proposes three kinds of measures to suppress the DDS spurious.The arbitrary signal generator is divided into the upper and lower computer. By the RS232 interface, the upper computer sends the control commands and signal data to the lower computer and achieves the control of lower computer. FPGA is the core control chip of the lower computer. FLASH stores the standard waveform data. SRAM is used to temporarily store the data which is sent from the upper computer and as the waveform buffer of the DDS. The lower computer uses phase accumulator to address SRAM and gets the amplitude data of the signal. Then it drives the D/A converter and low-pass filter to produce signals. Measuring the signals shows that the arbitrary signal generator meets the design requirement.