Abstract
In this paper a novel method to design a transformer based balun with isolation between output ports and matching characteristic at all ports is proposed. The main issue of transformer balun at millimeter-wave frequencies is that it has poor matching and isolation performance. In this work, an isolation circuit is introduced to place between output ports in the transformer balun design. As a validation, comparison has been made between the balun with and without isolation circuit, which has shown great performance improvement of proposed design. Moreover, design example is given for millimeter-wave on-chip implementation of this isolation circuit in standard silicon based technology with 6 metal layers.