Wing-integrated airborne antenna array beamforming sensitivity to wing deflections

For airborne radar, wing-integrated antenna arrays allow for large apertures in the cross-track direction. While large arrays have directivity and beamforming advantages, integrating the array onto the flexible structure introduces positional and phase center errors. Here we aim to characterize the radiation pattern sensitivity to the positional errors, and particularly the ability to form low sidelobe levels using the Chebyshev beamformer. As expected, the sidelobe level of arrays increase with increased deformation. The positional errors also result in main beam pointing error, increased beamwidth, and null degradation. We examined practical wing-integrated array sizes of 6-10 elements and found that when positional errors are normalized to the operating wavelength, the resulting pattern errors are frequency independent. In addition due to the limited array sizes examined, no significant correlation was found between increasing the number of elements in the array and changes in sidelobe level; however, there was a strong correlation between magnitude of the positional errors and the effects on sidelobe level. This was particularly true when trying to achieve very low sidelobes (40-60 dB). In an effort to compensate for errors caused by array deformation, a phase correction was applied to the patterns. It is shown that the pattern main beam could be corrected while the sidelobe levels could be decreased by up to 6 dB. To put this study in context, two fielded systems were investigated to determine actual wing deformation during flight.