On-Chip Rat-Race Balun with Stubs for Matching Arbitrary Terminal Impedances

An on-chip balun is useful in millimeter-wave integrated circuits. However, conventional baluns are unsuitable for the on-chip application because the terminal impedance is generally standardized by 50 Omega, which is not necessarily applies on a chip. Thus, we propose a novel on-chip rat-race balun with stubs for matching arbitrary terminal impedances. The on-chip balun with stubs is designed by applying the optimization method of two-port filters, and the characteristic of the balun is verified by a three-dimensional electromagnetic simulation.