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Wide Range Digitizer for Chem-Bio LIDAR

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Conference paper

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The Frequency Agile Laser FAL Sensor is an active standoff chemical detector, developed at The Edgewood Chemical Biological Center ECBC, for the purpose of remotely sensing chemical warfare agents. The Laser Standoff Chemical and Biological Detection LSCBD program is quite successful, however, one major limitation of the LSCBD system has been data acquisition and processing capability. The received analog signal, in a LIDAR system, is detected, amplified and digitized for subsequent computer processing. Typically, receiver amplifier gain is adjusted from time-to-time so that signal amplitude applied to the digitizer is not too large, resulting in a signal clipping, nor too small, resulting in poor digitizer resolution. In LIDAR applications, the received signal amplitude changes rapidly, and proper gain adjustment, in real-time, is difficult. The Laser Standoff Detection Group has addressed this problem by the design of a unique, high resolution, wide range digitizer. Four AD converters, each with a progressively higher voltage range, are configured in a circuit in which the input signal is applied simultaneously to all AD converters. Digital output signals are selected from the AD converter having the lowest voltage range, which is not exceeded by the input signal. These data comprise 16 bit data words, which are sent to a digital signal processor DSP. The DSP processes the LIDAR signal and sends data via a high-speed serial link to the LIDAR computer. This design eliminates the need for manual or automatic gain control amplifiers in the LIDAR data acquisition system. Digital signal resolution is maintained for small signals, yet large amplitude signals are not distorted due to signal clipping.

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  • Chemical, Biological and Radiological Warfare
  • Optical Detection and Detectors

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