Noncoherent Synthetic Aperture Imaging

Conclusion

The non coherent imaging technique does not aim at the same goal as the coherent synthesis. With the non coherent process, the overall resolution is not much increased with respect to the theoretical performance of the physical array. However, the image quality is definitively improved at a low computational expense, and without stringent requirements about the accuracy of the antennae trajectory and attitude.

The main interests for the non coherent synthesis are: 1) Reduction of the side lobe levels, together with a slight improvement of the resolution in azimuth; 2) Drastic reduction of the speckle effect so that objects whose size is close to the theoretical longitudinal resolution of the physical antennae can be detected; 3) Robustness of the image quality with respect to the trajectory and attitude artefacts; 4) Robustness of the image quality with respect to the vehicle speed as long as the redundancy factor remains larger than 5, which authorizes surveys at high coverage rate; 5) Improvement of bathymetric measurements through the redundancy factor. This effect will be shown in an other paper. We are looking now for an experiment carried from a vessel, in order to verify and to quantify the capabilities of this technique at larger ranges, i.e. in actual operational conditions.