A
grating
is an array of parallel obstructions separated from one another at a distance comparable to a wavelength. When an electromagnetic wave is incident up on a grating, it scatters to one or more specific angles determined by the spacing of the grating and the frequency of the wave. Since this effect is a diffraction phenomenon, gratings are often also referred to as
diffraction gratings
.
One of the most important uses of the diffraction grating is as an antenna for millimeter‐wave through optical frequencies. This type of diffraction grating is the primary focus of this article. In integrated optics, grating antennas are used to couple power into and out of dielectric waveguides. For millimeter‐wave systems, grating antennas have received attention for several key advantages that they have in comparison with other conventional microwave antennas. They have low radiation losses, they are inexpensive and easy to fabricate, and they are planar. There is also considerable interest in using grating antennas to implement low‐cost beam steering at millimeter‐wave frequencies.
This article examines gratings and grating antennas in a series of five sections. Each of these sections is presented in such a way that it may be read independently from the others. An overview of the historical development of diffraction gratings is presented. The fundamental principles behind grating diffraction are explained in a manner suitable for those with an RF/microwave background. A clear design procedure for grating antennas is offered, along with an extensive reference list for those interested in further study. Some of the latest and most impressive applications of millimeter‐wave gratings are described. The article then concludes with a brief discussion of the future of this field.
