Mitigation of wing flexure for airborne direction-finding applications

Calibration errors are the dominant error source for direction finding (DF) from airborne platforms. Calibration of the array manifold is done with the wings in an unknown position. Wing movements during flight perturbs the array manifold from its calibrated value, causing errors in the direction finding. We present a direction finding algorithm that compensates for variations in wing flexure. The algorithm relies on a physically motivated model that captures the gross behavior of the manifold perturbations. The model has been validated using experiments on a model aircraft in an anechoic chamber. The structure of the model can be exploited in estimation schemes such as weighted subspace fitting (WSF), leading to improved DF accuracy. With the correct model parameters, the effect of the manifold perturbation is, in fact, fully neutralized. The properties of the new scheme are demonstrated through analysis and simulation