FPGA based high precision sinusoidal signal generator

A 24-bit sigma-delta digital-to-analog converter(DAC)is used to produce high precision sinusoidal signals with low total harmonic distortion(usually less than-106dB)for seismic data acquisition system self-tests.The key problem is to convert the sinusoid to a sigma-delta bit stream to drive the sigma-delta DAC. This paper presents a field-programmable gate array(FPGA)based bit stream generator which is composed of a sinusoidal data memory, an interpolation filter and a sigma-delta modulator.This paper focuses on the design and simulation methods for the interpolation filter and the sigma-delta modulator and the whole system implementation using the DSP Builder in FPGA.Tests show that the bit stream generator can drive a 24-bit sigma-delta DAC to produce a 31.25Hz,3.96Vpeak-peak voltage sinusoidal signal with-121.0 dB total harmonic distortion and 111.4dB signal-to-noise ratio, which meets the needs for seismic use.The design is simple, programmable and easy to implement.