Miniaturized annular ring loaded patch antennas

The proliferation of wireless communication systems has promoted the development of miniaturized antenna designs. Annular ring patch antennas are reported to reduce antenna size. In this paper, several novel compact probe-fed annular-ring microstrip patch antennas are presented. In order to reduce the antenna size and provide a suitable input impedance match, two techniques are employed; the insertion of strips into the annular ring and placing a cross-slot into the ground plane. The proposed annular-ring patch antennas with a cross-slotted ground plane yield a much smaller size for a given frequency and are easily matched to 50 Ohms. These novel patch antennas can effectively be reduced by about 55 percent in size compared to conventional annular-ring patch antennas. The antenna can be designed for single band circular-polarization, dual-band circular polarization, triple band, or wideband operation, depending on parameter selection. Some significant advantages are evident for these structures, such as the centre-frequency exhibiting weak dependence on the position of the feedpoint as well as compact size. Good circularly polarized properties and wide CP bandwidths are obtained for these compact antennas. The multiband versions can provide small frequency ratios. The optimized dimensions for four different type antennas are displayed.