Integrated low-loss balun for Vivaldi antennas

A low-loss balun is presented that can be integrated on the low-permittivity substrates usually used in the construction of the adjoining Vivaldi antenna for improving the antenna radiation. However, it also increases the unwanted radiation of the feeding balun required for impedance matching and mode conversion. The radiation losses of the balun are reduced by limiting the size of balun, which is achieved by cladding the balun with slabs of high permittivity dielectric.