In order to solve the problem of the grating sensor displacement measurement system debugging

based on research on the principle of the output signal of the grating sensor

two channel sinusoidal signals which must be strictly orthogonal and same frequency are imitated by direct digital synthesis（DDS）technology.The basic principle of DDS is introduced

and the circuitry and the system of experiment are designed

and the experiments of testing are carried on.The experiment results indicate that frequency range of the system is 0.1Hz

2

0MHz

its errors of frequency and phase are less than 1%.The system structure is simple and the frequency modulation is easy and the requirement of measurement can be met.