A Planar Wideband Balanced Crossover

A planar wideband balanced crossover is presented in this paper. It consists of four balanced ports and two connected microstrip rings. Owing to its bisymmetry, even-odd mode analysis is utilized to derive the design equations. The property of transmission zeros of the differential-mode isolation is studied to facilitate the design of bandwidth. Explicit design equations and methodology are proposed and validated by measurement. A 2-GHz prototype has been fabricated and measured. For differential mode, the measured bandwidth of 15-dB return loss (RL), 1.3-dB insertion loss, and 20-dB isolation is 20%, which is four times of the bandwidth of the published balanced crossover. The bandwidth of 20-dB cross-mode isolation is 35%, which is almost triple of the bandwidth of the prior work. The presented crossover exhibits a bandwidth of 46.5% for 1-dB common-mode RL and shows wideband common-mode rejection as well.