Miniaturised wideband four-way out-of-phase power divider based on Marchand balun

A miniaturised wideband four-way out-of-phase power divider is presented in this study. The presented divider is developed based on a microstrip-line Marchand balun, which achieves the power-dividing function through the coupling between parallel microstrip lines (MLs). The coupling performance is improved by etching the rectangular-ring slots under the coupled MLs, which improved the operating bandwidth. The air-bridge resistance isolation circuit is used to improve the output impedance matching and isolation. Moreover, the even- and odd-mode equivalent-circuit method is applied to the presented power divider. The design has been verified by measurements, which show good agreements with simulations. The measured results show that the centre frequency is 3.4 GHz, the 15 dB input return loss bandwidth is >59.6%, and the output isolation is >15 dB.