A Single-Layer Planar Wideband Filtering Single-Ended-to-Balanced Crossover With Excellent Common-Mode Suppression

In this brief, a single-layer planar single-ended-to-balanced crossover has been proposed, which has a wideband filtering differential-mode response, wide path-isolation bandwidth, and an excellent common-mode suppression. The complete design procedure and rigorous derivations are demonstrated based on the even-/odd-mode analysis. A 3.5 GHz prototype has been designed, simulated and measured. Finally, the measured 15-dB differential-mode filtering bandwidth and 10-dB common-mode transmission bandwidth are 37.38% and 77.33%, respectively. Besides, a 117% bandwidth of 10-dB path-isolation is also achieved. Moreover, the bandwidth of 22-dB common-mode-to-differential-mode conversion is 143% over the frequency range of 1–6 GHz. This proposed crossover can be an excellent candidate for constructing balanced and unbalanced wireless communication systems.