Design of a new dual-band balun

In this paper, a novel dual-band balun with flexible frequency ratios will be presented. The proposed 3-port balun is based on a 4-port structure with the 4^th port terminated as an open end. Baluns transform unbalanced input signals to balanced output signals or vice versa. They have become very useful and needed in various applications such as balanced mixers, frequency multipliers, push-pull amplifiers, and antennas.