Lumped high-low pass balun for ultra wide band printed balanced antennas

A semi-lumped balun transformer for UHF dipoles is reported in this paper. The proposed structure utilizes two filters plus one small transmission line. This circuit does not require any multilayer either suspended substrates techniques. Its broadband behaviour is due to the use of lumped elements; this is particularly useful for low microwave band. The key idea is to use a geometrical progression for the characteristic line impedance and extract the values of the lumped elements from those values. Several baluns have been built to demonstrate the electrical feasibility in wideband UHF dipoles. Finally, a broadband monopole is attached to the balun to show its performance.