The uniform speed of the magnetic field is directly influenced by the quality of the exciting signals for time grating sensors, which determines the measurement accuracy of the time grating sensors. Therefore, the highquality exciting signals are of great significance to the measurement accuracy improvement of the time grating sensors. Regarding the high requirements on quadrature exciting signal sources for linear time grating sensors, a direct digital frequency synthesis technique is employed to design the quadrature exciting signals. In addition, an active band-pass filter is designed to eliminate the interference and improve the signal quality. The frequency and the phase of the proposed quadrature exciting signal sources can easily adjust, and the precision of the signals is high. The exciting signal sources and the signal processing circuits are integrated into one FPGA chip, which greatly decrease the size of the circuit board and improve the reliability. Simulation and experiment results prove the validity. This design method can be widely applied into many applications which require high quality of exciting signal sources.