Integrated-optical synthetic aperture radar processor

Abstract

Synthetic aperture radar (SAR) is a 2-D signal processing problem that normally requires a 3-D optical implementation. We describe an optical method for performing SAR imaging that can be implemented using integrated optics, which is typically configured as a planar structure. Two-dimensional signal processing is accomplished through a combination of spatial and temporal integration. The radar signal is entered into the integrated optical structure through a surface acoustic wave transducer and is first processed by spatial integration through 1-D diffraction within a uniform, planar optical waveguide. The spatially processed light is then coupled into an array of channel waveguides, which acts as a 1-D image dissector by expanding the light along the direction in which light propagates. The temporal integration takes place on a 2-D CCD detector array positioned on top of the channel waveguides. Light is selectively coupled vertically out of the waveguiding plane, with each channel waveguide illuminating a corresponding column of the CCD array through a 2-D spatially modulated transparency. Periodic transfer of the photogenerated charge on the CCD following each temporal integration period results in the formation of the focused radar image.