Dual-band BALUN design by The Series Connection of Wilkinson Power Divider and Phase Shifter

A reciprocal dual-band BALUN is designed by the series connection of a multi-stage Wilkinson power divider and a 180° phase shifter. The use of the word “reciprocal” is due to the fact that if the unbalanced input and balanced outputs are replaced, it also has a proper performance. As a proof of concept, a prototype model is fabricated and measured. The return loss is less than 10dB in the frequency bands 2.5 to 5.5 GHz and 10.1 to 13 GHz. The isolation between the balanced ports is better than -15dB. Simultaneously, the unbalance between the amplitudes and phases of balanced ports is less than 0.6 dB and , respectively. This BALUN is designed appropriately for TV satellite downlink.