Davarpanah M, Goben C A, Begley D L, Griffith S L
Appl Opt. 1976 Dec 1;15(12):3066-72. doi: 10.1364/AO.15.003066.
The excitation efficiencies for coupling surface electromagnetic waves onto aluminum at a microwave frequency (f = 8.445 GHz, lambda = 3.55 cm) were studied experimentally for several different standard microwave techniques as well as two optical techniques (prism and grating) applied to the microwave frequency region and two new techniques (hump and valley). The peak measured efficiencies found were: for the standard rectangular waveguide, 92%; for the horn antenna, 73%; for the right angle prism properly gapped above the metal, 60%; for the hump of 10-wavelength radius of curvature, 35%; for the thin grating strips on polystyrene coated metal, 30%; for the grating bars gapped (1/2) wavelength above the metal, 26%; and, for the valley of 10-wavelength radius, 12%. The measurement of the excitation efficiencies for prism and grating coupling techniques sometimes required that the prism or grating be in the near field of the antenna. In addition to measuring peak efficiencies, the efficiencies were measured as functions of the gap heights, the angular orientations, the different diffraction modes, the shapes, and the materials of the grating bars. The coupling efficiencies for both prism and grating couplers show a strong dependence on gap height above the metal. Dielectric grating bars were found to be inefficient compared to solid or hollow metallic bars, or thin metallic strips. The distance between the target point of the center line of the microwave horn antenna and the corner of the prism was found to be about 1 wavelength for maximum prism coupling efficiency.
针对几种不同的标准微波技术以及应用于微波频率区域的两种光学技术（棱镜和光栅）和两种新技术（驼峰和谷形），对在微波频率（f = 8.445 GHz，λ = 3.55 cm）下将表面电磁波耦合到铝上的激发效率进行了实验研究。测得的峰值效率如下：标准矩形波导为92%；喇叭天线为73%；在金属上方适当间隙的直角棱镜为60%；曲率半径为10个波长的驼峰为35%；聚苯乙烯涂层金属上的细光栅条为30%；在金属上方间隙为（1/2）波长的光栅条为26%；曲率半径为10个波长的谷形为12%。棱镜和光栅耦合技术激发效率的测量有时要求棱镜或光栅处于天线的近场中。除了测量峰值效率外，还测量了效率随间隙高度、角度取向、不同衍射模式、光栅条形状和材料的变化。棱镜和光栅耦合器的耦合效率都强烈依赖于金属上方的间隙高度。与实心或空心金属条或细金属条相比，发现介质光栅条效率较低。发现对于最大棱镜耦合效率，微波喇叭天线中心线的目标点与棱镜角之间的距离约为1个波长。
