Ultra-wideband unequal in-phase power divider using three-line coupled structure

A compact ultra-wideband in-phase power divider using a three-line coupled structure is proposed. The power division of the device depends on the coupling factors between the centreline and the two sidelines. For an enhanced isolation between the output ports, a 100 Ω chip resistor is connected between the ends of the two sidelines, whereas the end of the centre line is grounded. To verify the design, a prototype with 2:1 power division was fabricated and tested. The measured results validate the ultra-wideband performance with more than 12 dB return loss, more than 13 dB isolation and <;0.2 dB and 4° amplitude and phase imbalances, respectively, across the band 3.1-10.6 GHz.