Design of Accurately Modeled Direction-Finding Antenna Installations, 16-R9679

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Principal Investigator
Jason Polendo

Inclusive Dates:  01/01/07 – Current

Background - Shipboard radio direction-finding (DF) systems developed by SwRI are critically dependent on a stored table of characteristic antenna responses as functions of signal arriving direction and frequency. This table of antenna responses to controlled signals (dubbed the array manifold) has traditionally been generated by at-sea calibration measurements performed at extremely high cost. SwRI has been a pioneer in developing shipboard DF array manifolds from electromagnetic numerical models as a basis for reducing at-sea calibration measurements.

An apparent problem with numerically modeling these electromagnetically cluttered DF sites is the sensitivity of the installed antenna responses to inaccurate structural details. These structural details, geometric in nature, deviate from ship drawings and specifications even though such deviations may be within construction tolerances. Small deviations in nearby conducting structures can have a major impact on the response of the installed antenna. Installing antennas at locations that have reduced sensitivity to deviations in structural details will result in actual responses that better match the modeled responses, thereby reducing array manifold errors and improving DF performance.

Approach - The capabilities to be developed within this internal research project will enable the design of shipboard antenna arrays whose actual antenna responses maintain a high probability of agreement with those predicted by a numerical model even under the uncertain structural variability. Through the use of a developed surrogate numerical ship model, an iterative perturbation analysis will be completed to not only determine which geometrically uncertain ship structures are most influential to the individual antenna responses, but also to quantify the explicit impact structural variability has on each specific antenna site.

Accomplishments - Using a numerical model of a representative ship developed under this project whose construction was accomplished with the distinct intention of being conducive to an iterative perturbation analysis, an initial screening method has been completed to determine which ship structure distributions the antenna responses are most sensitive to. This reduced parameter space will be used for the quantification of the geometrical uncertainty within the individual antenna responses.

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