Patent ID: 6388739
Filing Date: 2002-05-14
Classification: G01H,G01P,G01S

Abstract:
A self-referencing microdoppler ladar receiver comprising:a frequency shifter for receiving a backscattered signal from a target that has been illuminated by a transmitter and for controllably shifting the frequency of the backscattered signal; an interferometer for directing portions of the frequency shifted signal along first and second paths of unequal length and for combining the portions of the frequency shifted signal to produce first and second output signals; and a signal processor for providing a feedback signal to control said frequency shifter based upon differences in the respective power levels of the first and second output signals such that said interferometer is driven towards quadrature, wherein the feedback signal provided by said signal processor is proportional to an instantaneous frequency of the backscattered signal including frequency contributions due to a vibrational velocity of the target such that the vibration of the target is detectable without a local reference derived from the transmitter.