A study has been made on near-field effect of extended target scattering in ground-bed active microwave remote sensing. The analysis is started from path-different-only coherent scattering case. The results show the predicted Fresnel zone interfering phenomenon. This somewhat explains why different measurement results may occur from different platform altitudes. Based on this analysis

we introduced the semi-rough scattering concept to cover more general practical cases.Results of this study may be a foundation for sensors calibration and ground-based accurate measurement in case of coherent extended targets.