FDTD analysis of dual frequency printed dipole antenna

The printed dipole antenna is adopted widely as a radiation element because array elements can be printed easily on a single substrate. The dipole antenna is usually fed by the balanced transmission line, while the coaxial cable, the un-balanced transmission line, is widely used for practical antenna systems. Therefore the balun is a mandatory component for the printed dipole antenna. We have reported the built-in balun antenna and its principle of feeding structure. The built-in balun antenna also reduces the antenna size for the normal dipole antenna. In this paper, we investigate the relations of this balun circuit and multifrequency operation. We also discuss the structure parameter of the built-in balun, and present a multifrequency antenna without the parasitic elements.