Time-delay detection of short pulses by Fresnel and Fourier transformations.
The Fresnel transform of a signal, when used as a preprocessing step to a subsequent spectrum analysis, helps to detect the time delay between short-pulse signals. Light from the short pulses disperses spatially as it propagates through free space to create an interference pattern. As the pulses move through an acousto-optic cell, a point photodetector produces a signal whose temporal frequency is directly proportional to the time delay between the pulses. When this signal is fed to a spectrum analyzer, the frequency domain represents a time-delay domain.
Vanderlugt
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Anderson
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Melsa
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