A dual polarized dual band microstrip antenna for wireless communications

The demand for antennas for mobile wireless applications has increased dramatically over the last 10 years. Today we have a number of land and satellite based systems for wireless communications using a wide range of frequency bands. Not only do we see an increase in the number of subscribers in the different systems but also a demand for dual or multi band equipment capable of handling two or more frequency bands. Our paper describes a dual polarized, dual band antenna element suited for use in a base station antenna. The antenna element is an aperture coupled, stacked patch, maintaining the symmetry needed for dual polarization operation. The total height is less than 0.15 /spl lambda/ at the lowest frequency and the element provides broadside radiation. Whereas most previously presented dual band elements are linearly polarized microstrip antennas which utilize a number of narrow-band resonators, our design has all the broadband and dual-polarized characteristics of traditional aperture coupled patch antennas. The bandwidth for return loss>10 dB of the element covers both the 880-960 MHz GSM (Global System for Mobile Communication) band and the 1710-1880 MHz DCS (Digital Cellular System) frequency band. The measured isolation between the ports corresponding to the two orthogonal polarizations is greater than 32 dB in both bands.