Balanced-to-Single-Ended Four-Way Out-of-Phase Power Divider and Its Application to Broadband Balanced Quasi-Yagi Antenna Array

A broadband balanced-to-single-ended (BTSE) four- way power divider (PD) with out-of-phase is designed in this letter. The proposed four-way PD composed of three-series T-junction PDs, a balanced U-type microstrip-slotline transition structure, and multiple cross-junction microstrip-slotline transitions. The series T-junction PD achieves equal amplitude and out-of-phase power distribution at the output ports over a wide frequency band. Meanwhile, the balanced U-type structure as the feed of the BTSE PD can realize a great broadband common-mode (CM) rejection without affecting the differential-mode (DM) responses. In addition, the proposed BTSE PD is employed with four quasi-Yagi antennas to realize a balanced quasi-Yagi antenna array. The proposed antenna array keeps the merits of wide DM transmission and high CM suppression level and achieves low cross-polarization level and high gain in the endfire direction. Finally, a prototype antenna array is fabricated and measured, and the experimental results show that it exhibits 10 dB return loss bandwidth of 5.7-8.9 GHz, peak gain of 12.5 dBi, and maximum cross-polarization levels of -25.6/-34.6 dB in E-/H-planes at 5.8 GHz, respectively.