ABSTRACT
This chapter examines the principles of geometrical optics followed by a brief discussion of the more general concept of physical optics. It argues that in many cases geometrical optics is inadequate to completely describe the behavior of the electromagnetic field and that it is necessary to include another field called the diffracted field. The well-known methods of optics have found increasing use in the treatmentof many electromagnetic problems when the wavelength is small compared to the size of the scatterer or antenna. Another example is the microstrip reflectarray which is a fairly new antenna concept. The feed antenna illuminates these patch elements, which are individually designed to scatter the incident field with the phase needed to form a constant aperture phase. The major portion of the antenna, reflecting surface, is a flat structure with a low profile. The antenna, a printed microstrip array, can be fabricated with a simple, low-cost etching process, especially when it is produced in large quantities.
