A new concept of an ultrawide bandwidth 180?-hybrid-coupler is presented. The ultrawideband design approach is based on the\nexcitation of a coplanar waveguide (CPW) mode and a coupled slot line (CSL) mode in the same double slotted planar waveguide.\nThecoupler is suitable for realization in planar printed circuit board technology. For verification of the new concept a prototype was\ndesigned for the frequency range from3GHz to 11GHz, built, andmeasured.Themeasurement results presented in this paper show\na good agreement between simulation and measurement and demonstrate the very broadband performance of the new device. The\ndemonstrated coupler with a size of 40mmÃ?â?? 55mm exhibits a fractional bandwidth of 114% centered at 7GHz with a maximum\namplitude imbalance of 0.8 dB and a maximum phase imbalance of 5?.
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