Four-element LC-baluns for power matching arbitrary impedances

Abstract Six four-element balun topologies are introduced that enable complex impedance matching in addition to common-mode rejection. Design equations for these topologies are presented. Three of these networks are universal, while the other three are capable of performing only specific impedance transformations. Examples of these networks were designed and fabricated along with a traditional lattice balun network for an operating frequency of 300 MHz. These networks were verified through extensive electromagnetic simulations and by measuring the fabricated networks. The fabricated novel network examples were able to achieve common-mode rejection ratios above 20 dB, power wave reflection coefficients below −20 dB, and insertion losses of approximately 0.1 dB; these results were similar to or better than the performance of the fabricated traditional lattice balun. The design example networks also provided power matching and low insertion loss over a greater bandwidth compared to the fabricated traditional network. These networks will allow for the footprints of lumped-element balun circuitry to be reduced, which is particularly useful in integrated circuit design. These topologies are also expected to further increase radio-frequency (RF) circuit design flexibility by offering more alternative realizations.