Bae Systems Information and Electronic Systems Integration Inc.

Wisterium Development LLC

Norman E Saucier

Norman D Paul

A system for calibrating airborne direction finding antenna arrays eliminates the problem of trying to maintain a constant depression angle when flying an airplane directly over a calibration antenna to collect deep depression angle data. The deep depression angle data necessary for calibration is provided by data from a scale model of the aircraft having a direction-finding array which simulates the actual direction-finding array on the aircraft. In order to collect deep depression angle data, the model is pivoted through 360&deg; while maintaining a controlled depression angle. Thus, it is unnecessary for calibration to actually fly a plane to attempt to obtain deep depression angle measurements. In the subject system, only a single depression set of data is required from the aircraft. Thus, with the exception of baseline shallow depression angle data from this plane, the calibration data comes strictly from the scale model, which is much more easily obtained. Optimization techniques are used in which a set of data is collected from the airplane at one shallow depression angle which is used with the data collected from the scale model at the same shallow depression angle to derive a complex set of optimized weights that are then applied to the data collected from the model at the remainder of the depression angles to obtain the appropriate database for use on this aircraft for direction finding. In so doing, the aircraft need only be flown to establish data at a relatively shallow depression angle which can be easily collected by an aircraft flying in circles or banana pattern at some distance from the calibration antenna.

Deep depression angle calibration of airborne direction finding arrays

A system is provided for reducing the time that a ship must be maintained on station to collect calibration data by reducing the frequencies at which calibration data is to be collected. Since it is impractical to consider calibrating over elevation angle and polarization on the full-scale ship, an accurate scale model and test facility are utilized, with surface wave data being collected from the ship before model-based data can be utilized. In the subject system, the number of calibration frequencies used aboard ship is dramatically reduced by as much as 80%, thus reducing the time the ship must be on station when doing a calibration run. In one embodiment, the shipboard surface wave data for one elevation and one polarization is combined with surface wave and sky wave data from the scale model to generate an array manifold or database used in subsequent direction finding activities. In order to minimize the frequencies at which shipboard data is collected, the set of frequencies used for shipboard calibration is limited to a subset of all the original calibration frequencies. The number of frequencies used for shipboard calibration is reduced by selecting frequencies which generate adjustment, or weighting factors which are valid over a wide bandwidth.

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New Ipswich, NH, United States of America

Norman E Saucier