The coupling efficiencies for the excitation of surface electromagnetic waves (SEW} for both the prism and the grating techniques have been studied experimentally in the microwave frequency range. The grating experiments included studies of the SEW coupling efficiencies as functions of the frequency, the angle of incidence, the grating constant, the number of grating bars, and the position of the grating bar at which the maximum radiation field of the antenna was aimed. For the prism coupling technique, the coupling efficiency was studied as functions of the angle of incidence, the aiming point of the transmitting antenna on the prism base, and the height of the prism above the metal strip or the standard railroad rail. The coupling efficiency for the prism coupling technique was found to be about 60 percent, whereas for the grating technique, the coupling efficiency was found to be about 15 percent. The coupling efficiencies for either coupling technique were found to be different for metal overlaid with thin dielectric materials and uncoated metal surfaces --Abstract, pages 2-3
