Investigation of Near-Field Electromagnetic Source Imaging Using Inverse Green's Function Integrations

摘要

As continued efforts are made to reduce the radar cross sections of aircraft and ships, designs are first modeled with computers and then tested in the lab. In the far-field of these tested objects, actual sources of high reflectivity or 'Hot Spots' on the tested objects can be isolated to within only one half the wavelength of the electromagnetic wave used for testing. Ideally, a probe could measure fields on the surface of the object being tested to completely isolate the source of the hot spot. Unfortunately, the presence of the probe on the surface of the object will disturb the very fields it is attempting to measure. Probe measurements made in the near field, close to but not on the object, can be designed to reduce the influence of the probe while providing accurate field data. The data thus measured, while not able to determine the source location perfectly, can be used to localize a source to less than one half wavelength, the far-field diffraction limit. This thesis tests a technique for back propagating computer generated near field measurements of an axisymmetric field source to determine the fields closer to the source. Several cases are examined that test the accuracy and resolving capability of the technique.