Theory of miniaturized shorting-post microstrip antennas

An analytical theory for the eigenfrequencies and eigenmodes of shorting-post microstrip antennas (MPA's) is presented. These antennas are seen as promising candidates for miniaturized mobile telecommunication handsets. In particular, it is shown that the zero mode of the unloaded MPA plays a central role for reducing the lowest operation frequency of the loaded MPA. The theory allows a complete calculation of all relevant antenna parameters and can easily be extended to the case of multiple shorting posts. Applications to the examples of rectangular and circular shorting post MPA's are illustrated.