Enhancement of Microstrip Monopole Antenna Bandwidth by Using EBG Structures

A novel compact design for UWB planar monopole antenna is presented in this letter. The basis for achieving the UWB operation is through using semicircular microstrip monopole antenna with circular modified ground plane. This shape produces bandwidth ranging from 3 to 35 GHz with discontinuities in certain bands from 7 to 10 GHz and from 12.5 to 17.5 GHz. The antenna size is around 27% of the size of a conventional rectangular microstrip patch antenna. Electromagnetic band-gap (EBG) structures are used for further improve the antenna performance. It is shown that by embedding metallo-EBG structure (MEBG) such as circular and square patches, it is possible to eliminate ripples in the operating band and still achieve a reduction in the antenna size to more than 60% from conventional patch. The final antenna design provides an impedance bandwidth (S11 $<{-}10$ dB) of more than 33 GHz with averaged radiation efficiency of 73%74% and antenna gain of 6.5 dBi.