Reduced size single and dual band linear polarized microstrip antennas for mobile communications

Two techniques to reduce the physical size of circular and rectangular microstrip patch antennas are presented. By utilizing the symmetry of the resonant current distribution, the size of the antenna can be reduced by one-half of the original patch. Second, slits are inserted within the antenna which are perpendicular to the resonant current. This forces the current to flow around the obstacles which has the effect of reducing the resonant frequency. Using slits, an antenna of one-fourth the area of the original patch can be realized. Lastly, using two patches displaced laterally or vertically an antenna with dual band capabilities can be realized. The two frequency bands, 1.8, 2.4 GHz and 5.2, 5.7 GHz, are chosen to lie within the existing PCS and Bluetooth bands and the two future Bluetooth frequency bands, respectively. The antenna geometry is an aperture coupled microstrip antenna. The reduced size and thin substrate thicknesses give compatibility with portable communications systems.