Printed antenna and microstrip technology: a brief review

Microstrip patch antennas are an example of a large class of modern antennas known as “printed antennas.” Microstrip was originally developed in the early 1950s as a transmission line, and the first publication on using this structure as a radiator appears to have been by Deschamp in 1953 [1, Section 1.1]. Almost 20 years then passed until the first patent of the modern microstrip antenna was registered in 1973 by Munson, although the structure was independently discovered in at least one other location.

Microstrip antennas are generally constructed using the same photo lithographic process used to create printed circuit boards. In their simplest form, radiation is due primarily to energy leaking out of the cavity formed by the patch located close to a ground plane; physically, the patch is simply a very wide microstrip line. For the basic rectangular patch, the radiation from two opposite sides reinforces, whereas that from the other two sides cancels. The patch is usually supported on a dielectric substrate of some form, primarily for structural reasons. Typical materials are Teflon and glass-reinforced plastics, as used in printed circuit board technology. Typical material properties for these are εr in the range from 2—2.5, and tan δ from 0.0004—0.002. High-εr substrates such as alumina ceramics produce physically small patches, but with very limited bandwidth. Typical material properties in this case are: εr 9.7—10.3, tan δ ≈ 0.0004. For some applications, plastic foam substrates have been used.