Microstrip Antennas

Abstract Microstrip antennas are probably the most popular type of planar antennas. Even though the basic microstrip element was invented in the early 50s, as a very narrow band (resonant) element, only in the last 15 years microstrip antennas have matured to the point that they are used in almost any application. Being low profile, lightweight, and relatively inexpensive, they are most suitable for military, space as well as commercial applications. Furthermore, with the latest developments in the wireless industry, the use of microstrip antennas increased exponentially. In the same time, the theoretical work done in the area of microstrip antennas produced more than 1500 published journal articles, numerous conference papers and six books. This chapter starts with the presentation of the rectangular microstrip patch antenna, which is widely used and lends itself to a simple, modal representation. It is inferred that most of the different geometries proposed along the years essentially behave like the rectangular patch with only minor differences in the electrical performance. Once the rectangular patch is fully characterized as a radiating element, different feeding techniques are presented. Then the polarizations characteristics as well as the bandwidth properties of microstrip antennas in general are discussed. Before the discussion on microstrip arrays, the mutual coupling problem is addressed. The last section of this chapter deals with microstrip arrays: topology, feeding networks and finally scanning arrays.