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The increase of terrorism and its global impact has made the screening of the contents of liquid-filled containers a
necessity. The ability to evaluate the contents of a container rapidly and accurately is a critical tool in maintaining global
safety and security. Due to the immense quantities and large variety of containers shipped worldwide, there is a need for
a technology that enables rapid and effective ways of conducting non-intrusive container inspections. Such inspections
can be performed utilizing "through-transmission" or "pulse-echo" acoustic techniques, in combination with multiple
frequency excitation pulses or waveforms. The challenge is combining and switching between the different acoustic
techniques without distorting the excitation pulse or waveform, degrading or adding noise to the receive signal; while
maintaining a portable, low-power, low-cost, and easy to use system.
The Pacific Northwest National Laboratory (PNNL) has developed a methodology and prototype device focused on this
challenge. The prototype relies on an advanced diplexer circuit capable of rapidly switching between both "through-transmission"
and "pulse-echo" detection modes. This type of detection requires the prototype to isolate the pulsing circuitry from the receiving circuitry to prevent damage and reduce noise.
The results of this work demonstrate that an advanced diplexer circuit can be effective; however, some bandwidth issues
exist. This paper focuses on laboratory measurements and test results acquired with the PNNL prototype device as
applied to several types of liquid-filled containers. Results of work conducted in the laboratory will be presented and
future measurement platform enhancements will be discussed.
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