A Systematic Method to Design Desired Wideband 180° Couplers

In this paper, a new method for designing the wideband 180° hybrids is presented. According to this method, a new wideband microstrip 180° hybrid is proposed. The structure consists of a combination of an Ultra-Wideband (UWB) phase shifter and four UWB Wilkinson power dividers (WPD). In the proposed configuration, the phase shifter and one WPD act as an out-of-phase power divider and other WPDs act as an in-phase power divider. The designed 180° hybrid coupler exhibits good wideband performance and has simple structure. The return loss of the sum port (Σ) and delta port (Δ) is less than -10 dB across the frequency band from 3 to 10.5 GHz and 2.7 to 9 GHz, respectively. The isolation between the output ports is better than 15 dB. Moreover, the phase deviation between the output ports is about ±5° for the out-of-phase power divider across the frequency band from 4 to 9.5 GHz.