Transmission Loss and Frequency-Angle-Time Spread: Issues and Model Analysis for the Littoral Warfare Advanced Development Focused Technology Experiment 96-1.
1997
Yang, T. C. | Al-Kurd, A. | Yates, T.
A mid-frequency active system concept was tested during the Focused Technology Experiment (FIE 96-1) sponsored by the Littoral Warfare Advanced Development (LWAD) program. Specifically, the BSDS directional projector was used as the source, an echo repeater was used to simulate the target, and the MUF (multiple frequency) volumetric array was used as the receiver. This report discusses modeled frequency, angle, and time spreading associated with one-way transmission loss, using the environmental parameters measured during the at-sea test. This modeling is intended to provide environmental acoustic support for the interpretation of the observed active detection performance and to help guide measurements made in future tests. We address issues such as source-receiver range and depths, propagation environments that impact the measurements of the transmission loss at mid frequencies in shallow waters, the difference in transmission loss using an omni-directional source versus that of a directional source (as used in some systems), the difference in model prediction between a normal mode and a PE model and its implications, and the advantages of using a continuous wave (CW) signal versus a broadband signal in the measurements of transmission loss and channel transfer function. These issues need to be examined for each experiment. Understanding of these issues with support from numerical analysis will significantly improve the quality of the data collection and help data interpretation. Candidate broadband signal waveforms and data analysis approach are discussed in an Appendix.
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