Abstract

This letter presents a compact reconfigurable multiband microstrip antenna. The multiplicity of bands is achieved by the use of concentric external metallic semirings around a central internal semicircular microstrip patch. These are all shorted to the ground plane via a vertical metallic wall through the common diametric plane, thereby adopting the concept of the planar inverted-F antenna (PIFA) for size reduction and thus compactness. The operation frequencies are tuned by varactor diodes placed between the inner semicircular patch and the outer half-rings. In addition to tunability, the overall bandwidth may also be widened by combining the tunable range. Theoretical simulations and measurements of manufactured prototypes agree well with each other.