A 6 to 20 GHz planar balun using a Wilkinson divider and Lange couplers

A simple broadband microstrip balun has been developed using a Wilkinson divider for power splitting followed by Lange couplers for phase shifting. This planar balun structure can be easily fabricated on an alumina substrate using a conventional MIC (microwave integrated circuit) process without the need for multilayer or suspended substrate techniques. The inherent wideband characteristics of the Wilkinson divider and Lange couplers and the symmetry of the structure have resulted in good broadband amplitude and phase balance performance. The balun fabricated on 10 mil alumina has an amplitude imbalance of +or-0.6 dB, average phase imbalance of 7 degrees , and a maximum total insertion loss of 1.2 dB from 6 to 20 GHz.<>