A Versatile Balun Based on a Power Divider Topology
Abstract
This paper presents an original balun concept based on a power divider topology. The proposed concept simplifies the design compared to a Marchand balun by eliminating the interconnection problem between the two couplers forming the Marchand balun. Furthermore, the proposed concept is highly versatile and allows for the straightforward realization of a double balun, with a single input and two differential outputs, without resorting to a cascade of differential power dividers. For simplicity, the concept is demonstrated in PCB technology using transdirectional couplers to overcome dimensional constraints associated with coupled-lines backward couplers, but this concept will be highly effective for balun design in CMOS technology in millimeter-wave bands beyond the hundred GHz range. The results lead to single-to-differential insertion loss of less than 0.5 dB at the operating frequency of 2 GHz, a return loss better than 15 dB, and a 3-dB bandwidth of around 40%.