Multi-Frequency and Dual-Mode Patch Antenna Based on Electromagnetic Band-gap (EBG) Structure

Microstrip patch antenna with multi-frequency and dual-mode is presented in this communication. The introduction of metamaterial substrate made of modified mushroom-type electromagnetic band-gap (EBG) structure enables the multi- functions. The composite right/left-handed transmission line (CRLH TL) theory and multi-conductor transmission line (MTL) theory are introduced to analyze and design this kind of antenna. Three modes including one monopolar radiation pattern in the n=0 mode and two patch-like radiation patterns in the n=-1, 1 modes respectively are analyzed and can be tuned by the parameters of the EBG structure. Since geometry of the radiating patch does not affect the infinite wavelength mode, circular polarization (CP) is obtained for the n=+1 mode by truncating the square radiating patch with linear polarization (LP) for the n=0 mode staying unchanged. Thus dual polarized antenna is obtained. Two prototypes of probe-fed patch antennas are fabricated to verify the theory analysis.