Mapping a diffraction field close to an obstacle

Demonstrates the effectiveness of the optically modulated scatterer technique as a probe for EMC measurements. As a practical test, the authors have measured the spatial distribution of the known microwave field caused by diffraction by a half-plane. The field was produced by directing linearly polarized 10 GHz radiation from a horn antenna on to the edge of a plane conducting sheet with an angle of incidence of approximately 45° and with the electric field parallel to the edge. The amplitude and phase of the electric field were measured on both sides of the sheet at distances from the edge down to a small fraction of a wavelength, and the results were compared with a modified form of Sommerfeld´s classical theory in which the source is a line current parallel to the edge. The spatial phase pattern matched well everywhere; in regions of small phase gradient the phase agrees to within 10°. The amplitude pattern was reproduced with an accuracy of about 5%