Square-ring pin-fed patch

Image of the Square-ring pin-fed patch.

Microstrip antennas, also called patch antennas, are very popular in the microwave frequency range because of their simplicity and compatibility with circuit board technology. They are usually operated near half-wave resonance to obtain a nominally real-valued input impedance. The fringing fields act to extend the effective length of the patch, thus, the length of the patch is usually less than a half wavelength in the dielectric medium. The pattern of a square patch antenna is broad with maximum direction normal to the plane of the antenna.

The centre frequency of a patch antenna can be lowered by removing a square area of metal from its centre. The resonant frequency and impedance bandwidth decreases while the input impedance increases by increasing the cut-out area. The reduction in resonant frequency for the same cut-out area is greater for thinner substrates