Airborne synthetic-aperture radar (SAR) systems employ coherent techniques to generate images of terrain in the microwave region of the spectrum. The high degree of coherence required by radar system considerations results in the presence of radar speckle when diffuse scatterers are imaged. It is possible to introduce frequency and/or angle diversity in such a manner that multiple uncorrelated images of the terrain may be generated and then summed incoherently to reduce the speckle. When system bandwidth and/or viewing angle is severely constrained, then a compromise must be made between image resolution and speckle reduction. Visual examination of controlled samples of radar imagery shows that speckle is reduced noticeably when incoherent summation of uncorrelated images is provided via use of diversity. Some examples of radar images with varying degrees of diversity are presented in the paper and are compared qualitatively.
© 1976 Optical Society of AmericaPDF Article