High resolution microwave imaging of the backscatter of a small tree and its variation with incidence angle

The work presented utilises a high resolution two dimensional imaging system to examine the interaction between X-band radar and biophysical objects in the near field. The imaging system produces two dimensional images in a format familiar to the human visual process and provides a detailed representation of the structure of the target. In-focus imagery is obtained by the application of a multifrequency algorithm which is developed from the traditional plane-to-plane diffraction technique. This algorithm has the advantage that it employs a narrower bandwidth than that normally associated with other multifrequency algorithms. Verification of the imaging system and performance of the algorithm are demonstrated by simulating a three dimensional test target. The system is then applied to the imaging of a small broad-leaved tree at 10 GHz. Measurements are made using a high precision vertical planar scanner located in an anechoic chamber. The effects of variation with angle are observed by positioning the tree to provide incidence angles in the range from 30° to 90°. These clearly demonstrate the sensitivity of the radar signal return to leaf incidence angle and other tree components