Reactively loaded microstrip antenna for dual-frequency operation

Novel dual-frequency operation of a single-feed rectangular microstrip antenna with an embedded reactive loading is presented. The reactive loading is provided by a structure of two cascaded microstrip-line sections embedded within a rectangular slot cut in the patch. By selecting suitable dimensions of the microstrip-line sections and the rectangular slot, the proposed antenna can perform a dual-frequency operation, with a low frequency ratio of about 1.04 to 1.15 between the two operating frequencies. Also, the two operation frequencies are of the same polarization planes and similar broadside radiation patterns.