Automatic gain control for the uniform amplitude of interferent signal in a Laser Doppler Vibrometer

The amplitude variation of the interferent signal can be caused since the object surface is uneven and the reaction angle can be varied according to the object motion. The amplitude variation causes an error in the signal processing algorithm. This error distorts the output signal. In order to eliminate this dependence of the interferent signal on the amplitude variation, two kinds of analog feedforward automatic gain control (AGC) which have more simple structure and higher bandwidth than that of the feedback method are proposed. Electronic circuits are constructed to implement the proposed AGC algorithms. The brief analysis, the measurement scheme of the system, and the experimental results of the AGCs using a laser Doppler vibrometer are presented. They demonstrate that the proposed AGCs are proven to make the system robust to the amplitude variation of the interferent signal