Millimeter-Wave Wideband Differential Four-Way Wilkinson Power Divider With 90° Rotational Symmetric Layout

This letter presents a four-way millimeter-wave differential Wilkinson power divider (WPD) with broadband characteristics using multisectional coupled inductors. To reduce the size effectively, one of the inductors is placed in a common path and the others in differential paths, which are mutually coupled with each other. It has a 90° rotational symmetric layout to minimize amplitude mismatches between channels. It shows a minimum insertion loss (IL) of 1.1 dB at 24 GHz and a peak isolation of 30 dB at 44 GHz. Over 20–44 GHz (~75% bandwidth), it also shows an IL of less than 1.8 dB and an isolation of greater than 14.5 dB. The measured input and output return losses show greater than 8 and 13.2 dB, respectively, in 20–44 GHz. The core chip is 0.35 mm $\times \,\, 0.41$ mm and is fabricated using a 65-nm RF CMOS process.