A compact dual-broadband microstrip antenna having both stacked and planar parasitic elements

It is possible for a single-element microstrip antenna to operate at two frequencies corresponding to two various resonant modes. The separation between the two frequency bands could be altered by placing shorting pins at the proper locations on the nodal lines of the fields of one of the modes. If both frequency bands are required to be too close to each other, at least, two patches have to be used simply by stacking them together. Using any of the above techniques, two separate narrow frequency bands may be obtained. However, in some antenna applications, the antenna is required to operate at two separate frequency broadbands. A very important example of such applications is the antenna used in cellular phones. Using a dual-band antenna having two separate bands, helps in eliminating the lossy expensive duplexer or at least making it cheaper and easier to design especially if two separate feeds could be used. A compact microstrip antenna has been developed for such an application. It consists of a driven element and five small parasitic patches distributed in two stacked layers. The two layers have similar geometries and their dimensions are almost equal.