Four-Element LC-Balun Topologies with Inherent DC-Feeding and DC-Blocking Properties and Complex Impedance Matching

In some applications, baluns need to provide useful DC characteristics, such as DC-blocking and DC-feeding in addition to common-mode rejection and impedance matching. This can be useful in handling DC biases without requiring extra biasing circuitry. The DC characteristics of three novel four-element complex conjugate matching LC-balun topologies as well as traditional lattice baluns are described in this paper. Design examples of the new four-element topologies were demonstrated experimentally. Traditional lattice networks were used for benchmarking. The novel four-element topologies exhibited similar or greater common-mode rejection while also providing power matching and useful DC characteristics.