Patch antenna

It consists of a planar rectangular or circular sheet or "patch" of metal, mounted over a larger sheet of metal called a ground plane.

It is the original type of microstrip antenna described by Howell in 1972.

[1] The two metal sheets together form a resonant piece of microstrip transmission line with a length of approximately one-half wavelength of the radio waves.

[2] The radiation at the edges causes the antenna to act slightly larger electrically than its physical dimensions, so in order for the antenna to be resonant, a length of microstrip transmission line slightly shorter than one-half the wavelength at the frequency is used.

It is widely used in portable wireless devices because of the ease of fabricating it on printed circuit boards.