DIFFRACTION NEAR FIELDS OF SMALL PHASE OBJECTS - COMPARISON OF 3-CM WAVE MEASUREMENTS WITH MOMENT-METHOD CALCULATIONS

Using a modified Mach-Zehnder interferometer for electromagnetic 3-cm waves, we measured the amplitude and phase distributions in the diffraction near fields of dielectric bars with rectangular cross sections (sizes smaller than 1 square wavelength, lambda) with high spatial resolution. Computer-controlled measurements were performed with high accuracy for distances 0.1-lambda-2-lambda behind the rear of the weak phase objects (phase shift DELTA-phi << 1 rad) that consist of foam materials (refractive index n = 1.02) or of thin plastic strips (n = 1.65, thickness d << lambda-). The experimental result agree with field computations made with the moment method.