Near-field of ground backscattering using a normal incident receiving antenna

In remote sensing applications, dimension of coverage area on the ground with a normal incident receiving antenna varies with the platform altitude of the sensor. Historically, the size of the coverage area has not been considered to calculate the far field condition due to the fact that the phases of the return wave from the area are not coherent. Here the author will show that although the phases are absolutely random, the near field effect still exists in a surface scattering case.