An Integrated Ultra-Wideband Balun Topology and Its Application in Mixer Design

A compact ultra-wideband balun topology suitable for on-chip integration is introduced in this paper. The balun is designed using an inverting transformer for the generation of the inverted signal, and a third inductor is incorporated to support the generation of the non-inverted signal. Through examining the transfer function and bandwidth limitations of existing on-chip voltage transformer and current transformer baluns, the broadband feature of the balun is clearly demonstrated through theoretical analysis and simulation, and further validated by a practical example. Measurement results confirm that a −3 dB relative bandwidth of approximately 167% is achieved, along with excellent amplitude and phase balance. The integrated ultra-wideband balun topology is also applied in a mixer design, resulting in a product with industry-leading RF and IF operating bandwidths.